diff --git a/pyproject.toml b/pyproject.toml
index 855693a..5a28a17 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -23,6 +23,8 @@ classifiers = [
 requires-python = ">=3.8"
 dependencies = [
     "bidsschematools >=0.9",
+    "attrs",
+    "httpx",
 ]
 
 [project.optional-dependencies]