Add the checkCompatibility API method as an MCP Tool #61

Describe the problem you are trying to solve:

Models sometimes have to make multiple API requests because their requests contain an incompatible set of dimensions and metrics.

Describe the solution you'd like:

Integrate the API's checkCompatibility method into the server. Possibilities include:

1. Add an MCP Tool so models can check for compatibility either proactively or after encountering an error.
2. In the existing runReport MCP Tool, add proactive checks or error handling that use checkCompatibility.