Update Vercel AI Gateway documentation

- Remove incorrect BYOK claim (not available in Roo Code)
- Add default model information (anthropic/claude-sonnet-4)
- Document prompt caching feature for Claude and GPT models
- Add model capabilities section (vision and tool support)
- Improve pricing clarity with model dropdown tip
- Add security and troubleshooting notes
- Document default temperature setting (0.7)
- Note that only language models are displayed
- Include API endpoint for technical reference

Author: hannesrudolph

docs/providers/vercel-ai-gateway.md

@@ -27,15 +27,28 @@ Useful links:
 
 ## Getting an API Key
 
-1.  **Sign Up/Sign In:** Go to the [Vercel Website](https://vercel.com/) and sign in Sign in.
+An API key is required for authentication.
+
+1.  **Sign Up/Sign In:** Go to the [Vercel Website](https://vercel.com/) and sign in.
 2.  **Get an API Key:** Go to the [API Key page](https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%2Fapi-keys&title=AI+Gateway+API+Key) in the AI Gateway tab. Create a new key.
 3.  **Copy the Key:** Copy the API key.
 
 ---
 
 ## Supported Models
 
-the Vercel AI Gateway supports a large and growing number of models.  Roo Code automatically fetches the list of available models. Refer to the [Vercel AI Gateway Models page](https://vercel.com/ai-gateway/models) for the complete and up-to-date list.
+The Vercel AI Gateway supports a large and growing number of models. Roo Code automatically fetches the list of available models from the `https://ai-gateway.vercel.sh/v1/models` endpoint. Only language models are shown.
+
+The default model is `anthropic/claude-sonnet-4` if no model is selected.
+
+Refer to the [Vercel AI Gateway Models page](https://vercel.com/ai-gateway/models) for the complete and up-to-date list.
+
+### Model Capabilities
+
+- **Vision Support**: Many models support image inputs.
+- **Tool/Computer Use**: Select models support function calling and computer use.
+
+Check the model description in the dropdown for specific capabilities.
 
 ---
 
@@ -48,9 +61,15 @@ the Vercel AI Gateway supports a large and growing number of models.  Roo Code a
 
 ---
 
+## Prompt Caching
+Vercel AI Gateway supports automatic prompt caching for select models including Anthropic Claude and OpenAI GPT models. This reduces costs by caching frequently used prompts.
+
+---
+
 ## Tips and Notes
 
-* **Model Selection:** OpenRouter offers a wide range of models. Experiment to find the best one for your needs.
-* **Pricing:** The Vercel AI Gateway charges based on the underlying model's pricing.  See the [Vercel AI Gateway Models page](https://vercel.com/ai-gateway/models) for details.
+* **Model Selection:** The Vercel AI Gateway offers a wide range of models. Experiment to find the best one for your needs.
+* **Pricing:** The Vercel AI Gateway charges based on the underlying model's pricing, including costs for cached prompts. See the [Vercel AI Gateway Models page](https://vercel.com/ai-gateway/models) for details.
+* **Temperature:** The default temperature is `0.7` and is configurable per model.
 * **Bring Your Own Key (BYOK):** The Vercel AI Gateway has **no markup** if you decide to use your own key for the underlying service.
 * **More info:** Vercel does not add rate limits. Upstream providers may. New accounts receive $5 credits every 30 days until the first payment.