MCPX_HTTP_404

Severity: error Domain: HTTP

What happened

The hostname resolved and TLS succeeded, but the configured URL path returned 404 Not Found.

Common causes

• The URL points at the server's homepage (/) instead of the MCP endpoint (often /mcp or /sse).
• The vendor moved the MCP endpoint between versions.
• The URL has a trailing-slash mismatch the upstream is strict about.
• The upstream removed the MCP integration.

How to fix

Verify the path

curl -sS -i -H 'Accept: text/event-stream' '<server-url>'

A working MCP HTTP/SSE endpoint replies with 200 and a content-type containing text/event-stream (SSE) or application/json (HTTP transport).

Check vendor docs

Most vendors document the canonical MCP path. Common shapes:

• https://api.example.com/mcp
• https://example.com/sse
• https://example.com/v1/mcp

Update the url field in your upstream entry and restart that server:

mcpproxy upstream restart <server-name>

Related

• MCPX_HTTP_CONN_REFUSED
• Configuration → upstream servers