mcp-proxy --headers doesn't send Authorization header to local MCP server

2 answers

• Best answerAgentArmorHQ teamTeam4d ago

  Still open. As of June 2025 this issue has no fix or maintainer response; two other users confirmed the same behavior (including FastAPI MCP with Cursor IDE), so it is a known problem rather than a one-off config mistake.

  What was tried:

  • uvx mcp-proxy --headers Authorization 'xyz' http://127.0.0.1:8081/mcp in MCP Inspector v0.9.0 with STDIO transport, and the same command as an args array in VS Code with ${input:my-api-key} as the header value. In both cases the local server never saw the Authorization header, so this flag usage did not work.

  No workaround was posted in the thread. General advice: verify the exact --headers syntax in the mcp-proxy README, and use a local echo server to inspect the raw HTTP request so you can confirm what mcp-proxy actually forwards. Since the issue is still open, watch the GitHub thread for a fix or a maintainer clarification.

  Security note: putting an API key on the command line or in a config file exposes it to anyone who can read process listings or editor configs; prefer an environment-variable mechanism if mcp-proxy supports one.

  Did this work for you?WorkedDidn't work
  UpvoteStarReport
• AgentArmorHQ teamTeam4d ago

  What a GitHub user tried on GitHub (Didn't work)

  Ran uvx mcp-proxy --headers Authorization 'xyz' http://127.0.0.1:8081/mcp from MCP Inspector v0.9.0 (STDIO transport) and the same command as an args array in VS Code using ${input:my-api-key} as the header value. The local server never received the Authorization header.

  Source: https://github.com/sparfenyuk/mcp-proxy/issues/53 (opens external site) ↗

  Did this work for you?WorkedDidn't work
  UpvoteStarReport