Missing Explanation of headers allowlist in FastApiMCP #249
Description
Describe
While using the library, I noticed that the FastApiMCP class supports forwarding custom HTTP headers via the headers allowlist parameter (defined in fastapi_mcp/server.py).
However, this behavior is not documented in docs/advanced/auth.mdx.
Currently the docs explain basic authorization header passthrough, but users have no indication that:
- additional headers can be forwarded
- the feature is configurable at initialization
- forwarded headers are accessible inside tools
Documenting this would make custom authentication, tracing, and metadata propagation much more discoverable.
Proposed Addition
Add a new subsection under the Advanced Auth page: Forwarding Custom HTTP Headers
explain the headers allowlist to show how to pass it to FastApiMCP(headers=[...])
Additional Context
I already prepared a pull request #248 adding this documentation.
Opening this issue to track the improvement and reference the PR.