diff --git a/lib/stripe.ex b/lib/stripe.ex
index b5b699d..461c350 100644
--- a/lib/stripe.ex
+++ b/lib/stripe.ex
@@ -28,41 +28,50 @@ defmodule Stripe do
       STRIPE_SECRET_KEY=YOUR_SECRET_KEY
   """
 
-  defp get_secret_key do
+  defp get_secret_key(opts) do
+    Keyword.get(opts, :secret_key) ||
     System.get_env("STRIPE_SECRET_KEY") || 
     Application.get_env(:stripe, :secret_key) || 
     raise AuthenticationError, message: @missing_secret_key_error_message
   end
 
-  defp request_url(endpoint) do
-    Path.join(@api, endpoint)
-  end
-
   defp request_url(endpoint, []) do
     Path.join(@api, endpoint)
   end
 
-  defp request_url(endpoint, data) do
+  defp request_url(endpoint, params) do
     base_url = request_url(endpoint)
-    query_params = Stripe.Utils.encode_data(data)
+    query_params = Stripe.Utils.encode_data(params)
     "#{base_url}?#{query_params}"
   end
 
-  defp create_headers(opts) do
+  defp create_headers(request_opts) do
     headers = 
-      [{"Authorization", "Bearer #{get_secret_key()}"},
+      [{"Authorization", "Bearer #{get_secret_key(opts)}"},
        {"User-Agent", "Stripe/v1 stripe-elixir/#{@client_version}"},
        {"Content-Type", "application/x-www-form-urlencoded"}]
 
-    case Keyword.get(opts, :stripe_account) do 
+    case Keyword.get(request_opts, :stripe_account) do 
       nil -> headers 
       account_id -> [{"Stripe-Account", account_id} | headers]
     end
   end
 
-  def request(action, endpoint, data, opts) when action in [:get, :post, :delete] do
-    HTTPoison.request(action, request_url(endpoint, data), "", create_headers(opts))
-    |> handle_response
+  def request(%Stripe.Request{method: method, endpoint: endpoint, params: params}, request_opts \\ []) do
+    HTTPoison.request(
+      method, 
+      request_url(endpoint, params), 
+      <<>>, 
+      create_headers(request_opts)
+    )
+    |> handle_response()
+  end
+
+  def request!(%Stripe.Request{} = request_struct, opts \\ []) do 
+    case request(request_struct, opts) do 
+      {:ok, result} -> result 
+      {:error, error} -> raise error
+    end
   end
 
   defp handle_response({:ok, %{body: body, status_code: 200}}) do
diff --git a/lib/stripe/api.ex b/lib/stripe/api.ex
index cc5289e..6b69adc 100644
--- a/lib/stripe/api.ex
+++ b/lib/stripe/api.ex
@@ -1,53 +1,8 @@
 defmodule Stripe.API do
-  defmacro __using__(opts) do
-    quote do
-      if :create in unquote(opts) do
-        @doc """
-        Create a(n) #{__MODULE__ |> to_string |> String.split(".") |> List.last}
-        """
-        def create(data, opts \\ []) do
-          Stripe.request(:post, endpoint(), data, opts)
-        end
-      end
-
-      if :retrieve in unquote(opts) do
-        @doc """
-        Retrive a(n) #{__MODULE__ |> to_string |> String.split(".") |> List.last} by its ID
-        """
-        def retrieve(id, opts \\ []) when is_bitstring(id) do
-          resource_url = Path.join(endpoint(), id)
-          Stripe.request(:get, resource_url, [], opts)
-        end
-      end
-
-      if :update in unquote(opts) do
-        @doc """
-        Update a(n) #{__MODULE__ |> to_string |> String.split(".") |> List.last}
-        """
-        def update(id, data, opts \\ []) do
-          resource_url = Path.join(endpoint(), id)
-          Stripe.request(:post, resource_url, data, opts)
-        end
-      end
-
-      if :list in unquote(opts) do
-        @doc """
-        List all #{__MODULE__ |> to_string |> String.split(".") |> List.last}s
-        """
-        def list(pagination_opts \\ [], opts \\ []) when is_list(pagination_opts) do
-          Stripe.request(:get, endpoint(), pagination_opts, opts)
-        end
-      end
-
-      if :delete in unquote(opts) do
-        @doc """
-        Delete a(n) #{__MODULE__ |> to_string |> String.split(".") |> List.last}
-        """
-        def delete(id, data \\ [], opts \\ []) when is_bitstring(id) do
-          resource_url = Path.join(endpoint(), id)
-          Stripe.request(:delete, resource_url, data, opts)
-        end
-      end
-    end
-  end
+  @callback list(pagination_opts :: Enum.t) :: Stripe.Request.t
+  @callback retrieve(id :: binary) :: Stripe.Request.t 
+  @callback create(Enum.t) :: Stripe.Request.t
+  @callback update(id :: binary, updates :: Enum.t) :: Stripe.Request.t 
+  @callback delete(id :: binary, options :: Enum.t) :: Stripe.Request.t
+  @optional_callbacks list: 1, retrieve: 1, create: 1, update: 2, delete: 2
 end
diff --git a/lib/stripe/balance.ex b/lib/stripe/balance.ex
index c3a4221..3cffc5e 100644
--- a/lib/stripe/balance.ex
+++ b/lib/stripe/balance.ex
@@ -1,11 +1,20 @@
 defmodule Stripe.Balance do
-  use Stripe.API, [:list]
+  @moduledoc""" 
+  Functions related to get balance information
+  """
 
+  @behaviour Stripe.API
+
+  @spec endpoint :: binary
   def endpoint do
     "balance"
   end
 
+  @spec retrieve() :: Stripe.Request.t
   def retrieve do
-    list
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint()
+    }
   end
 end
diff --git a/lib/stripe/balance_transaction.ex b/lib/stripe/balance_transaction.ex
index 5a70f04..7eab3f6 100644
--- a/lib/stripe/balance_transaction.ex
+++ b/lib/stripe/balance_transaction.ex
@@ -1,11 +1,29 @@
 defmodule Stripe.BalanceTransaction do
-  use Stripe.API, [:retrieve, :list]
+  @moduledoc"""
+  Functions related for balance history
+  """
 
-  def endpoint do
-    "balance/history"
+  @behaviour Stripe.API
+
+  @spec endpoint(binary) :: binary
+  def endpoint(id \\ "") do
+    "balance/history/#{id}"
+  end
+
+  @spec retrieve(binary) :: Stripe.Request.t
+  def retrieve(balance_id) do 
+    %Stripe.Request{
+      method: :get, 
+      endpoint: endpoint(balance_id)
+    }
   end
 
-  def all(opts \\ []) do
-    list([], opts)
+  @spec all(Enum.t) :: Stripe.Request.t
+  def all(pagination_opts \\ []) do 
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(),
+      params: pagination_opts
+    }
   end
 end
diff --git a/lib/stripe/bitcoin_receiver.ex b/lib/stripe/bitcoin_receiver.ex
index 746185f..b978c4c 100644
--- a/lib/stripe/bitcoin_receiver.ex
+++ b/lib/stripe/bitcoin_receiver.ex
@@ -1,6 +1,4 @@
 defmodule Stripe.BitcoinReceiver do
-  use Stripe.API, [:create, :retrieve, :list]
-
   def endpoint do
     "bitcoin/receivers"
   end
diff --git a/lib/stripe/charge.ex b/lib/stripe/charge.ex
index 0a6df6c..a814c27 100644
--- a/lib/stripe/charge.ex
+++ b/lib/stripe/charge.ex
@@ -1,15 +1,54 @@
 defmodule Stripe.Charge do
-  use Stripe.API, [:list, :retrieve, :create, :update]
+  @moduledoc"""
+  Functions related to charges
+  """
+  @behaviour Stripe.API
 
-  def endpoint do
-    "charges"
+  @spec endpoint(binary) :: binary
+  def endpoint(id \\ "") do
+    "charges/#{id}"
   end
 
-  def capture_endpoint(id) do
-    "#{endpoint()}/#{id}/capture"
+  @spec list(Enum.t) :: Stripe.Request.t
+  def list(pagination_opts \\ []) do 
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(),
+      params: pagination_opts
+    }
+  end
+  
+  @spec retrieve(binary) :: Stripe.Request.t
+  def retrieve(charge_id) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(charge_id)
+    }
+  end
+
+  @spec create(Enum.t) :: Stripe.Request.t
+  def create(params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(),
+      params: params
+    }
+  end
+
+  @spec update(binary, Enum.t) :: Stripe.Request.t
+  def update(charge_id, params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(charge_id),
+      params: params
+    }
   end
 
-  def capture(id, opts \\ []) do
-    Stripe.request(:post, capture_endpoint(id), [], opts)
+  @spec capture(binary) :: Stripe.Request.t
+  def capture(charge_id) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: "#{endpoint()}/#{charge_id}/capture"
+    }
   end
 end
diff --git a/lib/stripe/connect/account.ex b/lib/stripe/connect/account.ex
index 4d23346..a9ad2c5 100644
--- a/lib/stripe/connect/account.ex
+++ b/lib/stripe/connect/account.ex
@@ -1,38 +1,114 @@
 defmodule Stripe.Account do
-  use Stripe.API, [:create, :retrieve, :update, :list, :delete]
+  @moduledoc"""
+  Functions related to connect accounts
+  """
 
-  def endpoint, do: "accounts"
+  @behaviour Stripe.API
 
-  def reject(account_id, [reason: reason], opts \\ []) do
-    Stripe.request(:post, "#{endpoint()}/#{account_id}/reject", [reason: reason], opts)
+  @spec endpoint(binary) :: binary
+  def endpoint(account_id \\ "") do 
+    "accounts/#{account_id}"
   end
 
+  @spec list(Enum.t) :: Stripe.Request.t
+  def list(pagination_opts \\ []) do 
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(),
+      params: pagination_opts
+    }
+  end
+
+  @spec retrieve(binary) :: Stripe.Request.t
+  def retrieve(account_id) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(account_id)
+    }
+  end
+
+  @spec create(Enum.t) :: Stripe.Request.t
+  def create(params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(),
+      params: params
+    }
+  end
+
+  @spec update(binary, Enum.t) :: Stripe.Request.t
+  def update(account_id, params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(account_id),
+      params: params
+    }
+  end
+
+  @spec delete(binary) :: Stripe.Request.t
+  def delete(account_id) do
+    %Stripe.Request{
+      method: :delete,
+      endpoint: endpoint(account_id)
+    }
+  end
+
+  @spec reject(binary, Enum.t) :: Stripe.Request.t
+  def reject(account_id, params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: "#{endpoint(account_id)}/reject",
+      params: params
+    }
+  end
+
+  # external accounts
+
+  @spec external_account_endpoint(binary) :: binary
   def external_account_endpoint(account_id, external_account_id \\ "") do 
-    "#{endpoint()}/#{account_id}/external_accounts/#{external_account_id}"
+    "#{endpoint(account_id)}/external_accounts/#{external_account_id}"
   end 
 
-  def create_external_account(account_id, [external_account: token_id], opts \\ []) do
-    url = external_account_endpoint(account_id)
-    Stripe.request(:post, url, [external_account: token_id], opts)
+  @spec list_external_account(binary, Enum.t) :: Stripe.Request.t
+  def list_external_account(account_id, pagination_opts \\ []) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: external_account_endpoint(account_id),
+      params: pagination_opts
+    }
   end
 
-  def retrieve_external_account(account_id, external_account_id, opts \\ []) do
-    url = external_account_endpoint(account_id, external_account_id)
-    Stripe.request(:get, url, [], opts)
+  @spec retrieve_external_account(binary, binary) :: Stripe.Request.t
+  def retrieve_external_account(account_id, external_account_id) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: external_account_endpoint(account_id, external_account_id)
+    }
   end
 
-  def update_external_account(account_id, external_account_id, updates, opts \\ []) do
-    url = external_account_endpoint(account_id, external_account_id)
-    Stripe.request(:post, url, updates, opts)
+  @spec create_external_account(binary, Enum.t) :: Stripe.Request.t
+  def create_external_account(account_id, params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: external_account_endpoint(account_id),
+      params: params
+    }
   end
 
-  def delete_external_account(account_id, external_account_id, opts \\ []) do
-    url = external_account_endpoint(account_id, external_account_id)
-    Stripe.request(:delete, url, [], opts)
+  @spec update_external_account(binary, binary, Enum.t) :: Stripe.Request.t
+  def update_external_account(account_id, external_account_id, params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: external_account_endpoint(account_id, external_account_id),
+      params: params
+    }
   end
 
-  def list_external_account(account_id, pagination_opts \\ [], opts \\ []) do
-    url = external_account_endpoint(account_id)
-    Stripe.request(:get, url, pagination_opts, opts)
+  @spec delete_external_account(binary, binary) :: Stripe.Request.t
+  def delete_external_account(account_id, external_account_id) do
+    %Stripe.Request{
+      method: :delete,
+      endpoint: external_account_endpoint(account_id, external_account_id)
+    }
   end
 end
diff --git a/lib/stripe/connect/application_fee.ex b/lib/stripe/connect/application_fee.ex
index 9b745ea..82e640d 100644
--- a/lib/stripe/connect/application_fee.ex
+++ b/lib/stripe/connect/application_fee.ex
@@ -1,15 +1,60 @@
 defmodule Stripe.ApplicationFee do
-  use Stripe.API, [:create, :retrieve, :update, :list]
+  @behaviour Stripe.API
 
-  def endpoint do
-    "application_fees"
+  @spec endpoint(binary) :: binary
+  def endpoint(application_fee_id \\ "") do
+    "application_fees/#{application_fee_id}"
   end
 
-  def refund(fee_id, opts \\ []) do
-    Stripe.request(:post, "#{endpoint()}/#{fee_id}/refund", [], opts)
+  @spec list(Enum.t) :: Stripe.Request.t
+  def list(pagination_opts \\ []) do 
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(),
+      params: pagination_opts
+    }
+  end
+  
+  @spec retrieve(binary) :: Stripe.Request.t
+  def retrieve(application_fee_id) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(application_fee_id)
+    }
+  end
+
+
+  @spec create(Enum.t) :: Stripe.Request.t
+  def create(params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(),
+      params: params
+    }
+  end
+
+  @spec update(binary, Enum.t) :: Stripe.Request.t
+  def update(application_fee_id, params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(application_fee_id),
+      params: params
+    }
+  end
+
+  # refunds
+
+  def refund(fee_id) do
+    %Stripe.Request{
+      method: :post,
+      endpint: "#{endpoint(fee_id)}/refund"
+    }
   end
 
   def retrieve_refund(fee_id, refund_id, opts \\ []) do
-    Stripe.request(:get, "#{endpoint()}/#{fee_id}/refund/#{refund_id}", [], opts)
+    %Stripe.Request{
+      method: :get,
+      endpint: "#{endpoint(fee_id)}/refund/#{refund_id}"
+    }
   end
 end
diff --git a/lib/stripe/connect/country_spec.ex b/lib/stripe/connect/country_spec.ex
index bc97c5d..9e2bb66 100644
--- a/lib/stripe/connect/country_spec.ex
+++ b/lib/stripe/connect/country_spec.ex
@@ -1,7 +1,29 @@
 defmodule Stripe.CountrySpec do
-  use Stripe.API, [:retrieve, :list]
+  @moduledoc"""
+  Functions related to connect country specs.
+  """
 
-  def endpoint do
-    "country_specs"
+  @behaviour Stripe.API
+
+  @spec endpoint(binary) :: binary
+  def endpoint(country_spec_id) do
+    "country_specs/#{country_spec_id}"
+  end
+
+  @spec list(Enum.t) :: Stripe.Request.t
+  def list(pagination_opts \\ []) do 
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(),
+      params: pagination_opts
+    }
+  end
+  
+  @spec retrieve(binary) :: Stripe.Request.t
+  def retrieve(country_spec_id) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(country_spec_id)
+    }
   end
 end
diff --git a/lib/stripe/connect/recipient.ex b/lib/stripe/connect/recipient.ex
index 972b939..c6f752e 100644
--- a/lib/stripe/connect/recipient.ex
+++ b/lib/stripe/connect/recipient.ex
@@ -1,7 +1,55 @@
 defmodule Stripe.Recipient do
-  use Stripe.API, [:create, :retrieve, :update, :delete, :list]
+  @moduledoc"""
+  Functions related to recipents
+  """
 
-  def endpoint do
-    "recipients"
+  @behaviour Stripe.API
+
+  @spec endpoint(binary) :: binary
+  def endpoint(recipient_id \\ "") do
+    "recipients/#{recipient_id}"
+  end
+
+  @spec list(Enum.t) :: Stripe.Request.t
+  def list(pagination_opts \\ []) do 
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(),
+      params: pagination_opts
+    }
+  end
+  
+  @spec retrieve(binary) :: Stripe.Request.t
+  def retrieve(recipient_id) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(recipient_id)
+    }
+  end
+
+  @spec create(Enum.t) :: Stripe.Request.t
+  def create(params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(),
+      params: params
+    }
+  end
+
+  @spec update(binary, Enum.t) :: Stripe.Request.t
+  def update(recipient_id, params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(recipient_id),
+      params: params
+    }
+  end
+
+  @spec delete(binary) :: Stripe.Request.t
+  def delete(recipient_id) do
+    %Stripe.Request{
+      method: :delete,
+      endpoint: endpoint(recipient_id)
+    }
   end
 end
diff --git a/lib/stripe/customer.ex b/lib/stripe/customer.ex
index f46647d..d04c9df 100644
--- a/lib/stripe/customer.ex
+++ b/lib/stripe/customer.ex
@@ -1,73 +1,145 @@
 defmodule Stripe.Customer do
-  use Stripe.API, [:retrieve, :update, :create, :list, :delete]
-
-  def endpoint do
-    "/customers"
+  @moduledoc"""
+  Functions related to a customer
+  """
+  @behaviour Stripe.API
+
+  @spec endpoint(binary) :: binary
+  def endpoint(id \\ "") do
+    "/customers/#{id}"
   end
 
-  # discount
-
-  def delete_discount(customer_id, opts \\ []) do
-    Stripe.request(:delete, "#{endpoint()}/#{customer_id}/discount", [], opts)
+  @spec list(Enum.t) :: Stripe.Request.t
+  def list(pagination_opts \\ []) do 
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(),
+      params: pagination_opts
+    }
   end
-
-  # sources
-
-  def retrieve_source(customer_id, source_id, opts \\ []) do
-    Stripe.request(:get, "#{endpoint()}/#{customer_id}/sources/#{source_id}", [], opts)
+  
+  @spec retrieve(binary) :: Stripe.Request.t
+  def retrieve(customer_id) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(customer_id)
+    }
   end
 
-  def update_source(customer_id, source_id, updates, opts \\ []) do
-    Stripe.request(:post, "#{endpoint()}/#{customer_id}/sources/#{source_id}", updates, opts)
+  @spec create(Enum.t) :: Stripe.Request.t
+  def create(params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(),
+      params: params
+    }
   end
 
-  def create_source(customer_id, data, opts \\ []) do
-    Stripe.request(:post, "#{endpoint()}/#{customer_id}/sources", data, opts)
+  @spec update(binary, Enum.t) :: Stripe.Request.t
+  def update(customer_id, params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(customer_id),
+      params: params
+    }
   end
 
-  def delete_source(customer_id, data, opts \\ []) do
-    Stripe.request(:delete, "#{endpoint()}/#{customer_id}/sources/#{data[:source]}", [], opts)
+  @spec delete(binary) :: Stripe.Request.t
+  def delete(customer_id) do
+    %Stripe.Request{
+      method: :delete,
+      endpoint: endpoint(customer_id)
+    }
   end
 
-  # card
+  # discount
 
-  def create_card(customer_id, card_id, opts \\ []) do
-    create_source(customer_id, [source: card_id], opts)
-  end
+  @spec delete_discount(binary) :: Stripe.Request.t
+  def delete_discount(customer_id) do
+    %Stripe.Request{
+      method: :delete,
+      endpoint: "#{endpoint(customer_id)}/discount"
+    }
+  end 
 
-  def update_card(customer_id, card_id, updates) do
-    update_source(customer_id, card_id, updates)
+  # sources
+
+  @spec list_sources(binary, Enum.t) :: Stripe.Request.t 
+  def list_sources(customer_id, pagination_opts \\ []) do 
+    %Stripe.Request{
+      method: :get,
+      endpoint: "#{endpoint(customer_id)}/sources",
+      params: pagination_opts
+    }
   end
 
-  def delete_card(customer_id, card_id, opts \\ []) do
-    delete_source(customer_id, [source: card_id], opts)
+  @spec retrieve_source(binary, binary) :: Stripe.Request.t 
+  def retrieve_source(customer_id, source_id) do 
+    %Stripe.request{
+      method: :get,
+      endpoint: "#{endpoint(customer_id)}/sources/#{source_id}"
+    }
   end
 
-  def list_cards(customer_id, pagination_opts \\ [], opts \\ []) do
-    pagination_opts = put_in(pagination_opts, [:object], "card")
-    Stripe.request(:get, "#{endpoint()}/#{customer_id}/sources", pagination_opts, opts)
+  @spec create_source(binary, params) :: Stripe.Request.t
+  def create_source(customer_id, params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: "#{endpoint(customer_id)}/sources",
+      params: params
+    }
   end
 
-  # bank_account
+  @spec update_source(binary, binary, params) :: Stripe.Request.t
+  def update_source(customer_id, source_id, params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: "#{endpoint(customer_id)}/sources/#{source_id}",
+      params: params
+    }
+  end
 
-  def create_bank_account(customer_id, bank_acct_id, opts \\ []) do
-    create_source(customer_id, [source: bank_acct_id], opts)
+  @spec delete_source(binary, binary) :: Stripe.Request.t
+  def delete_source(customer_id, source_id) do
+    %Stripe.Request{
+      method: :delete,
+      endpoint: "#{endpoint(customer_id)}/sources/#{source_id}"
+    }
   end
 
-  def update_bank_account(customer_id, bank_acct_id, updates, opts \\ []) do
-    update_source(customer_id, bank_acct_id, updates, opts)
+  @spec list_cards(binary, Enum.t) :: Stripe.Request.t
+  def list_cards(customer_id, pagination_opts \\ []) do
+    list_sources(customer_id, pagination_opts)
+    |> put_in([:params, :object], "card")
   end
 
-  def delete_bank_account(customer_id, bank_acct_id, opts \\ []) do
-    delete_source(customer_id, [source: bank_acct_id], opts)
+  @spec create_card(customer_id, card_id) :: Stripe.Request.t 
+  def create_card(customer_id, card_id) do
+    create_source(customer_id, [source: card_id])
   end
 
-  def list_bank_accounts(customer_id, pagination_opts \\ [], opts \\ []) do
-    pagination_opts = put_in(pagination_opts, [:object], "bank_account")
-    Stripe.request(:get, "#{endpoint()}/#{customer_id}/sources", pagination_opts, opts)
+  @spec update_card(binary, binary, Enum.t) :: Stripe.Request.t
+  def update_card(customer_id, card_id, updates) do
+    update_source(customer_id, card_id, updates)
   end
 
-  def verify_bank_account(customer_id, bank_acct_id, amounts, opts \\ []) do
-    Stripe.request(:post, "#{endpoint()}/#{customer_id}/sources/#{bank_acct_id}/verify", [amounts: amounts], opts)
+  @doc """ 
+  Verify a bank account using two small deposit amounts (in cents). 
+
+      Stripe.Customer.verify_bank_account("cus_DKdfmidqL", "bank_dWIKSdlwi", [19, 29])
+      |> Stripe.request!
+  """
+  @spec verify_bank_account(binary, binary, list :: Stripe.Request.t
+  def verify_bank_account(customer_id, bank_acct_id, amounts) do 
+    %Stripe.Request{
+      method: :post,
+      endpoint: "#{endpoint(customer_id)}/sources/#{bank_acct_id}/verify",
+      params: [amounts: amounts]
+    }
+
+  @spec list_bank_accounts(binary, binary) :: Stripe.Request.t
+  def list_bank_accounts(customer_id, pagination_opts \\ []) do
+    list_sources(customer_id, pagination_opts)
+    |> put_in([:params, :object], "bank_account")
   end
 end
diff --git a/lib/stripe/dispute.ex b/lib/stripe/dispute.ex
index 747b671..2325cd4 100644
--- a/lib/stripe/dispute.ex
+++ b/lib/stripe/dispute.ex
@@ -1,15 +1,50 @@
 defmodule Stripe.Dispute do
-  use Stripe.API, [:list, :create, :update]
+  @behaviour Stripe.API
 
-  def endpoint do
-    "disputes"
+  @spec endpoint(binary) :: binary
+  def endpoint(dispute_id \\ "") do
+    "disputes/#{dispute_id}"
   end
 
-  def close_dispute_endpoint(id) do
-    "#{endpoint()}/#{id}/close"
+  @spec list(Enum.t) :: Stripe.Request.t
+  def list(pagination_opts \\ []) do 
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(),
+      params: pagination_opts
+    }
+  end
+  
+  @spec retrieve(binary) :: Stripe.Request.t
+  def retrieve(dispute_id) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(dispute_id)
+    }
+  end
+
+  @spec create(Enum.t) :: Stripe.Request.t
+  def create(params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(),
+      params: params
+    }
+  end
+
+  @spec update(binary, Enum.t) :: Stripe.Request.t
+  def update(dispute_id, params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(dispute_id),
+      params: params
+    }
   end
 
-  def close(id, opts \\ []) do
-    Stripe.request(:post, close_dispute_endpoint(id), [], opts)
+  def close(dispute_id) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: "#{endpoint(dispute_id)}/close"
+    }
   end
 end
diff --git a/lib/stripe/event.ex b/lib/stripe/event.ex
index 4bc1b4b..32d1a72 100644
--- a/lib/stripe/event.ex
+++ b/lib/stripe/event.ex
@@ -1,7 +1,29 @@
 defmodule Stripe.Event do
-  use Stripe.API, [:retrieve, :list]
+  @moduledoc"""
+  Functions related to events
+  """
 
-  def endpoint do
-    "events"
+  @behaviour Stripe.API
+
+  @spec endpoint(binary, binary) :: Stripe.Request.t
+  def endpoint(event_id \\ "") do
+    "events/#{event_id}"
+  end
+
+  @spec list(Enum.t) :: Stripe.Request.t
+  def list(pagination_opts \\ []) do 
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(),
+      params: pagination_opts
+    }
+  end
+  
+  @spec retrieve(binary) :: Stripe.Request.t
+  def retrieve(event_id) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(event_id)
+    }
   end
 end
diff --git a/lib/stripe/file.ex b/lib/stripe/file.ex
index c2fc1d6..c5b57d4 100644
--- a/lib/stripe/file.ex
+++ b/lib/stripe/file.ex
@@ -1,7 +1,34 @@
 defmodule Stripe.File do
-  use Stripe.API, [:create, :retrieve, :list]
+  @behaviour Stripe.API
 
-  def endpoint do
-    "files"
+  @spec endpoint(binary) :: binary
+  def endpoint(file_id \\ "") do
+    "files/#{file_id}"
+  end
+
+  @spec list(Enum.t) :: Stripe.Request.t
+  def list(pagination_opts \\ []) do 
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(),
+      params: pagination_opts
+    }
+  end
+  
+  @spec retrieve(binary) :: Stripe.Request.t
+  def retrieve(file_id) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(file_id)
+    }
+  end
+
+  @spec create(Enum.t) :: Stripe.Request.t
+  def create(params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(),
+      params: params
+    }
   end
 end
diff --git a/lib/stripe/refund.ex b/lib/stripe/refund.ex
index 97a4ed6..359a08f 100644
--- a/lib/stripe/refund.ex
+++ b/lib/stripe/refund.ex
@@ -1,7 +1,47 @@
 defmodule Stripe.Refund do
-  use Stripe.API, [:create, :retrieve, :update, :list]
+  @moduledoc""" 
+  Functions related to refunds.
+  """
 
-  def endpoint do
-    "refunds"
+  @behaviour Stripe.API
+  
+  @spec endpoint(binary) :: binary
+  def endpoint(refund_id \\ "") do
+    "refunds/#{refund_id}"
+  end
+
+  @spec list(Enum.t) :: Stripe.Request.t
+  def list(pagination_opts \\ []) do 
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(),
+      params: pagination_opts
+    }
+  end
+  
+  @spec retrieve(binary) :: Stripe.Request.t
+  def retrieve(refund_id) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(refund_id)
+    }
+  end
+
+  @spec create(Enum.t) :: Stripe.Request.t
+  def create(params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(),
+      params: params
+    }
+  end
+
+  @spec update(binary, Enum.t) :: Stripe.Request.t
+  def update(refund_id, params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(refund_id),
+      params: params
+    }
   end
 end
diff --git a/lib/stripe/request.ex b/lib/stripe/request.ex
new file mode 100644
index 0000000..f499002
--- /dev/null
+++ b/lib/stripe/request.ex
@@ -0,0 +1,13 @@
+defmodule Stripe.Request do 
+  defstruct [
+    method: nil,
+    endpoint: nil,
+    params: []
+  ]
+
+  @type t :: %{
+    method: :get | :post | :delete,
+    endpoint: binary,
+    params: list() | map()
+  }
+end
\ No newline at end of file
diff --git a/lib/stripe/subscriptions/coupon.ex b/lib/stripe/subscriptions/coupon.ex
index 1e46687..82c00e1 100644
--- a/lib/stripe/subscriptions/coupon.ex
+++ b/lib/stripe/subscriptions/coupon.ex
@@ -1,7 +1,55 @@
 defmodule Stripe.Coupon do
-  use Stripe.API, [:create, :retrieve, :update, :delete, :list]
+  @moduledoc"""
+  Functions related to coupons
+  """
 
-  def endpoint do
-    "coupons"
+  @behaviour Stripe.API
+
+  @spec endpoint(binary) :: binary
+  def endpoint(coupon_id) do
+    "coupons/#{coupon_id}"
+  end
+
+  @spec list(Enum.t) :: Stripe.Request.t
+  def list(pagination_opts \\ []) do 
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(),
+      params: pagination_opts
+    }
+  end
+  
+  @spec retrieve(binary) :: Stripe.Request.t
+  def retrieve(coupon_id) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(coupon_id)
+    }
+  end
+
+  @spec create(Enum.t) :: Stripe.Request.t
+  def create(params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(),
+      params: params
+    }
+  end
+
+  @spec update(binary, Enum.t) :: Stripe.Request.t
+  def update(coupon_id, params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(coupon_id),
+      params: params
+    }
+  end
+
+  @spec delete(binary) :: Stripe.Request.t
+  def delete(coupon_id) do
+    %Stripe.Request{
+      method: :delete,
+      endpoint: endpoint(coupon_id)
+    }
   end
 end
diff --git a/lib/stripe/subscriptions/invoice.ex b/lib/stripe/subscriptions/invoice.ex
index c892968..b36c224 100644
--- a/lib/stripe/subscriptions/invoice.ex
+++ b/lib/stripe/subscriptions/invoice.ex
@@ -1,23 +1,39 @@
 defmodule Stripe.Invoice do
-  use Stripe.API, [:create, :retrieve, :update, :list]
+  @behaviour Stripe.API
 
-  def endpoint do
-    "invoices"
+  @spec endpoint(binary) :: binary
+  def endpoint(invoice_id \\ "") do
+    "invoices/#{invoice_id}"
   end
 
+  @spec line_items(Enum.t) :: Stripe.Request.t
   def line_items(%{"id" => invoice_id}) do
     line_items(invoice_id)
   end
-
-  def line_items(invoice_id, pagination_opts \\ [], opts \\ []) do
-    Stripe.request(:get, "#{endpoint()}/#{invoice_id}/lines", pagination_opts, opts)
+  
+  @spec retrieve_line_items(binary, Enum.t) :: Stripe.Request.t
+  def line_items(invoice_id, pagination_opts \\ []) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: "#{endpoint(invoice_id)}/lines",
+      params: pagination_opts
+    }
   end
 
-  def upcoming(data, opts \\ []) do
-    Stripe.request(:get, "#{endpoint()}/upcoming", data, opts)
+  @spec upcoming(Enum.t) :: Stripe.Request.t
+  def upcoming(params) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: "#{endpoint()}/upcoming",
+      params: params
+    }
   end
 
-  def pay(invoice_id, opts \\ []) do
-    Stripe.request(:post, "#{endpoint()}/#{invoice_id}/pay", [], opts)
+  @spec pay(binary) :: Stripe.Request.t
+  def pay(invoice_id) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: "#{endpoint(invoice_id)}/pay"
+    }
   end
 end
diff --git a/lib/stripe/subscriptions/invoice_item.ex b/lib/stripe/subscriptions/invoice_item.ex
index bf8549d..d4ccb83 100644
--- a/lib/stripe/subscriptions/invoice_item.ex
+++ b/lib/stripe/subscriptions/invoice_item.ex
@@ -1,7 +1,55 @@
 defmodule Stripe.InvoiceItem do
-  use Stripe.API, [:create, :retrieve, :update, :delete, :list]
+  @moduledoc""" 
+  Functions related to invoice items
+  """
 
-  def endpoint do
-    "invoiceitems"
+  @behaviour Stripe.API
+
+  @spec endpoint(binary) :: binary
+  def endpoint(invoice_item_id \\ "") do
+    "invoiceitems/#{invoice_item_id}"
+  end
+
+  @spec list(Enum.t) :: Stripe.Request.t
+  def list(pagination_opts \\ []) do 
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(),
+      params: pagination_opts
+    }
+  end
+  
+  @spec retrieve(binary) :: Stripe.Request.t
+  def retrieve(invoice_item_id) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(invoice_item_id)
+    }
+  end
+
+  @spec create(Enum.t) :: Stripe.Request.t
+  def create(params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(),
+      params: params
+    }
+  end
+
+  @spec update(binary, Enum.t) :: Stripe.Request.t
+  def update(invoice_item_id, params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(invoice_item_id),
+      params: params
+    }
+  end
+
+  @spec delete(binary) :: Stripe.Request.t
+  def delete(invoice_item_id) do
+    %Stripe.Request{
+      method: :delete,
+      endpoint: endpoint(invoice_item_id)
+    }
   end
 end
diff --git a/lib/stripe/subscriptions/plan.ex b/lib/stripe/subscriptions/plan.ex
index b696d3b..afbfd5d 100644
--- a/lib/stripe/subscriptions/plan.ex
+++ b/lib/stripe/subscriptions/plan.ex
@@ -1,7 +1,55 @@
 defmodule Stripe.Plan do
-  use Stripe.API, [:create, :retrieve, :update, :delete, :list]
+  @moduledoc"""
+  Functions related to subscription plans.
+  """
 
-  def endpoint do
-    "plans"
+  @behaviour Stripe.API
+
+  @spec endpoint(binary) :: binary
+  def endpoint(plan_id) do
+    "plans/#{plan_id}"
+  end
+
+  @spec list(Enum.t) :: Stripe.Request.t
+  def list(pagination_opts \\ []) do 
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(),
+      params: pagination_opts
+    }
+  end
+  
+  @spec retrieve(binary) :: Stripe.Request.t
+  def retrieve(plan_id) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(plan_id)
+    }
+  end
+
+  @spec create(Enum.t) :: Stripe.Request.t
+  def create(params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(),
+      params: params
+    }
+  end
+
+  @spec update(binary, Enum.t) :: Stripe.Request.t
+  def update(plan_id, params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(plan_id),
+      params: params
+    }
+  end
+
+  @spec delete(binary) :: Stripe.Request.t
+  def delete(plan_id) do
+    %Stripe.Request{
+      method: :delete,
+      endpoint: endpoint(plan_id)
+    }
   end
 end
diff --git a/lib/stripe/subscriptions/subscription.ex b/lib/stripe/subscriptions/subscription.ex
index 2814030..baab510 100644
--- a/lib/stripe/subscriptions/subscription.ex
+++ b/lib/stripe/subscriptions/subscription.ex
@@ -1,11 +1,63 @@
 defmodule Stripe.Subscription do
-  use Stripe.API, [:create, :retrieve, :update, :delete, :list]
+  @moduledoc"""
+  Functions related to subscriptions
+  """
 
-  def endpoint do
-    "subscriptions"
+  @behaviour Stripe.API
+
+  @spec endpoint(binary) :: binary
+  def endpoint(subscription_id \\ "") do
+    "subscriptions/#{subscription_id}"
+  end
+
+  @spec list(Enum.t) :: Stripe.Request.t
+  def list(pagination_opts \\ []) do 
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(),
+      params: pagination_opts
+    }
+  end
+  
+  @spec retrieve(binary) :: Stripe.Request.t
+  def retrieve(subscription_id) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(subscription_id)
+    }
+  end
+
+  @spec create(Enum.t) :: Stripe.Request.t
+  def create(params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(),
+      params: params
+    }
+  end
+
+  @spec update(binary, Enum.t) :: Stripe.Request.t
+  def update(subscription_id, params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(subscription_id),
+      params: params
+    }
+  end
+
+  @spec delete(binary) :: Stripe.Request.t
+  def delete(subscription_id, options \\ []) do
+    %Stripe.Request{
+      method: :delete,
+      endpoint: endpoint(subscription_id),
+      params: options
+    }
   end
 
-  def delete_discount(subscription_id, opts \\ []) do
-    Stripe.request(:delete, "#{endpoint()}/#{subscription_id}/discount", [], opts)
+  def delete_discount(subscription_id) do
+    %Stripe.Request{
+      method: :delete,
+      endpoint: "#{endpoint(subscription_id)}/discount"
+    }
   end
 end
diff --git a/lib/stripe/token.ex b/lib/stripe/token.ex
index 155f56e..08d77c5 100644
--- a/lib/stripe/token.ex
+++ b/lib/stripe/token.ex
@@ -1,7 +1,38 @@
 defmodule Stripe.Token do
-  use Stripe.API, [:create, :retrieve]
+  @moduledoc"""
+  Functions related to tokens
+  """
 
-  def endpoint do
-    "tokens"
+  @behaviour Stripe.API
+
+  @spec endpoint(binary) :: binary
+  def endpoint(token_id \\ "") do 
+    "tokens/#{token_id}"
+  end
+
+  @spec list(Enum.t) :: Stripe.Request.t
+  def list(pagination_opts \\ []) do 
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(),
+      params: pagination_opts
+    }
+  end
+  
+  @spec retrieve(binary) :: Stripe.Request.t
+  def retrieve(token_id) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(token_id)
+    }
+  end
+
+  @spec create(Enum.t) :: Stripe.Request.t
+  def create(params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(token_id),
+      params: params
+    }
   end
 end
diff --git a/lib/stripe/transfer.ex b/lib/stripe/transfer.ex
index cec70c7..ad2feca 100644
--- a/lib/stripe/transfer.ex
+++ b/lib/stripe/transfer.ex
@@ -1,27 +1,87 @@
 defmodule Stripe.Transfer do
-  use Stripe.API, [:create, :retrieve, :update, :list]
+  @moduledoc""" 
+  Functions related to transfers.
+  """
 
-  def endpoint do
-    "transfers"
+  @behaviour Stripe.API
+
+  @spec endpoint(binary) :: binary 
+  def endpoint(transfer_id \\ "") do
+    "transfers/#{transfer_id}"
+  end
+
+  @spec list(Enum.t) :: Stripe.Request.t
+  def list(pagination_opts \\ []) do 
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(),
+      params: pagination_opts
+    }
+  end
+  
+  @spec retrieve(binary) :: Stripe.Request.t
+  def retrieve(transfer_id) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: endpoint(transfer_id)
+    }
   end
 
-  def transfer_reversal_endpoint(transfer_id, reversal_id \\ "") do
-    "#{endpoint()}/#{transfer_id}/reversals/#{reversal_id}"
+  @spec create(Enum.t) :: Stripe.Request.t
+  def create(params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(),
+      params: params
+    }
   end
 
-  def create_reversal(transfer_id, data \\ [], opts \\ []) do
-    Stripe.request(:post, transfer_reversal_endpoint(transfer_id), data, opts)
+  @spec update(binary, Enum.t) :: Stripe.Request.t
+  def update(transfer_id, params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: endpoint(transfer_id),
+      params: params
+    }
   end
 
-  def retrieve_reversal(transfer_id, reversal_id, opts \\ []) do
-    Stripe.request(:get, transfer_reversal_endpoint(transfer_id, reversal_id), [], opts)
+  @spec reversal_endpoint(binary, binary) :: binary
+  def reversal_endpoint(transfer_id, reversal_id \\ "") do
+    "#{endpoint(transfer_id)}/reversals/#{reversal_id}"
   end
 
-  def update_reversal(transfer_id, reversal_id, data, opts \\ []) do
-    Stripe.request(:post, transfer_reversal_endpoint(transfer_id, reversal_id), data, opts)
+  @spec list_reversals(binary, Enum.t) :: Stripe.Request.t
+  def list_reversals(transfer_id, pagination_opts \\ []) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: reversal_endpoint(),
+      params: pagination_opts
+    }
+  end
+
+  @spec create_reversals(binary, Enum.t) :: Stripe.Request.t
+  def create_reversal(transfer_id, params) do
+    %Stripe.Request{
+      method: :post,
+      endpoint: reversal_endpoint(),
+      params: params
+    }
+  end
+  
+  @spec retrieve_reversals(binary, binary) :: Stripe.Request.t
+  def retrieve_reversal(transfer_id, reversal_id) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: reversal_endpoint(transfer_id, reversal_id)
+    }
   end
 
-  def list_reversals(transfer_id, pagination_opts, opts \\ []) do
-    Stripe.request(:get, transfer_reversal_endpoint(transfer_id), pagination_opts, opts)
+  @spec update_reversal(binary, binary, Enum.t) :: Stripe.Request.t
+  def update_reversal(transfer_id, reversal_id, params) do
+    %Stripe.Request{
+      method: :get,
+      endpoint: reversal_endpoint(transfer_id, reversal_id),
+      params: params
+    }
   end
 end
diff --git a/lib/stripe/utils.ex b/lib/stripe/utils.ex
index 2e8e438..338c5e8 100644
--- a/lib/stripe/utils.ex
+++ b/lib/stripe/utils.ex
@@ -7,7 +7,7 @@ defmodule Stripe.Utils do
   Encodes the given map or list of tuples.
   Borrowed from "https://github.com/elixir-lang/plug/blob/master/lib/plug/conn/query.ex"
   """
-  def encode_data(kv, encoder \\ &to_string/1) do
+  def encode_params(kv, encoder \\ &to_string/1) do
    IO.iodata_to_binary encode_pair("", kv, encoder)
   end