handle invalid no arg in tool

[huozhi]

This PR is to avoid LLM calling docs mcp tool without any query, it should always have a query

⏺ I'll call the Next.js docs tool without any arguments.
  ⎿  Error: MCP error -32603: Tool execution failed: Invalid arguments - query: Invalid input: expected
     string, received undefined

⏺ The query parameter is required for the Next.js docs tool. It expects a search query string. Would
  you like me to:

  1. Call it with a specific search query?
  2. Try searching for general documentation?
  3. Something else?

Closes NXT-88