MCP server URL trailing slash 404: use mcp.sume.com/mcp

Configure the Sume hosted MCP server as https://mcp.sume.com/mcp, exactly, with no trailing slash. The server code registers the POST route at /mcp, and I found no redirect from /mcp/ in the MCP server source, so a client option about following redirects will not fix a wrong URL.

Sume facts are from the MCP overview and quickstart and the MCP server source, read 2026-10-01.

What does the MCP Python SDK 2.2.0 change about redirects?

The release notes say client redirects are only followed within the endpoint's origin: same scheme, host and port, or an http to https upgrade on the same host. They also say the follow_redirects setting on a passed-in httpx2.AsyncClient is no longer used for MCP requests, so you do not need it for the trailing-slash redirect. That describes servers that answer a slash variant with a redirect. It says nothing about servers that do not.

Which URL form does Sume accept?

How do I fix a 404 on the MCP URL?

Copy the URL from the docs rather than retyping it, then check the config for a trailing slash, a path added by a template, or a base URL joined to /mcp twice. After saving, call mcp_health or tools_list, as the quickstart suggests, to confirm the endpoint, auth source and safety posture.

What if the URL is right and I still get an error?

Then look at auth. An unauthenticated or under-scoped session returns auth errors, not a missing route. See the discover RPC post for what the endpoint returns, and Claude Code's authentication prompt for sign-in problems.