MCP: 405 Method Not Allowed

[EskelCz]

When trying to connect to the MCP server on localhost, the connection is refused:
The process logs this:

"POST /mcp/sse HTTP/1.1" 405 Method Not Allowed

I'm using this MCP config for Claude Desktop (tried Claude Code as well, same issue):

  "mcpServers": {
    "seller-agent": {
      "command": "uvicorn",
      "args": ["ad_seller.interfaces.api.main:app", "--port", "8000"],
      "headers": {
        "Authorization": "Bearer ... my API key"
      },
      "env": {
        "ANTHROPIC_API_KEY": "... my Anthropic key"
      }
    }
  }

Am I missing something?

[EskelCz]

Supposedly this is the root of the issue:

This app currently mounts FastMCP’s legacy SSE transport, while modern Claude integrations often use streamable HTTP semantics (POST to the configured URL)

This part of the documentation is misleading:
https://iabtechlab.github.io/seller-agent/guides/claude-desktop-setup/#option-b-local-development-server

Workaround is to use the mcp-remote project.
Better approach would be to update the MCP server in this project to use stdio for local setup.