fix: use actual tool description instead of type

[bebiksior]

When defining tools in the AI SDK

export const sendRequestTool = tool({
  description: "Send the current HTTP request for this replay session",
  inputSchema: z.object({}),
  execute: async () => {},
});

According to the OpenRouter docs, the description should be sent in the tools[].function.description field so the model knows when and how to use the tool

Currently, the OpenRouter provider sends tool.type instead of the actual description, resulting in requests like this

This PR updates the provider to send the correct description value, matching the behavior described in the OpenRouter docs and used by other ai sdk providers

[louisgv]

Thanks for the fix 🙏

[mutewinter]

Just wanted to say that this was a catastrophic bug for us, and you should shout from the hilltops that people need to upgrade from the beta to fix this behavior.