clarity on how to add openrouter for llm-support

README.md

@@ -119,6 +119,61 @@ You can find a lot more about configuring Grist, setting up authentication,
 and running it on a public server in our
 [Self-Managed Grist](https://support.getgrist.com/self-managed/) handbook.
 
+## Using Grist with OpenRouter for Model Agnostic and Claude Support
+
+Grist's AI Formula Assistant can be configured to use OpenRouter instead of connecting directly to OpenAI, allowing you to access a wide range of AI models including Anthropic's Claude models. This isn't the only way to use Claude models, but it's a good option if you want to use Claude models with Grist or intend to use other cheaper, faster, or potentially newer models. That's because this configuration gives you more flexibility in choosing the AI model that works best for your formula generation needs.
+To set up OpenRouter integration, configure the following environment variables:
+
+### Required: Set the endpoint to OpenRouter's API
+
+```
+ASSISTANT_CHAT_COMPLETION_ENDPOINT=https://openrouter.ai/api/v1/chat/completions
+```
+
+### Required: Your OpenRouter API key
+
+```
+ASSISTANT_API_KEY=your_openrouter_api_key_here
+```
+
+Sign up for an OpenRouter API key at <https://openrouter.ai/>
+
+### Optional: Specify which model to use (examples below)
+
+```
+ASSISTANT_MODEL=anthropic/claude-3.7-sonnet
+```
+
+### or other options like
+
+```
+ASSISTANT_MODEL=deepseek/deepseek-r1-zero:free
+```
+
+```
+ASSISTANT_MODEL=qwen/qwq-32b:free
+```
+
+```
+ASSISTANT_MODEL=mistralai/mistral-saba
+```
+
+### Optional: Set a larger context model for fallback
+
+```
+ASSISTANT_LONGER_CONTEXT_MODEL=anthropic/claude-3-opus-20240229
+```
+
+With this configuration, Grist's AI Formula Assistant will route requests through OpenRouter to your specified model. This allows you to:
+
+Access Anthropic's Claude models which excel at understanding context and generating accurate formulas
+Switch between different AI models without changing your Grist configuration
+Take advantage of OpenRouter's routing capabilities to optimize for cost, speed, or quality
+
+You can find the available models and their identifiers on the OpenRouter website.
+Note: Make sure not to set the OPENAI_API_KEY variable when using OpenRouter, as this would override the OpenRouter configuration.
+
+
 ## Available Docker images
 
 The default Docker image is `gristlabs/grist`. This contains all of