Inferrex

/ mcp probe

The Inferrex MCP probe.

A small, polite crawler that keeps the tool lists in Inferrex's library of MCP servers current. It sends unauthenticated, read-only requests, and you can opt out.

/ what it is

Why it contacted your server.

Inferrex keeps a library of MCP servers that records how each server signs in and which tools it lists. The probe re-checks the hosted servers in that library — the ones that publish an HTTPS endpoint, from Inferrex's own curated list and from the MCP Registry — so that record stays current.

It is identified by its User-Agent and by the client name it gives in the MCP handshake:

User-Agent: inferrex-mcp-probe/1 (+https://inferrex.com/mcp-probe)
MCP clientInfo.name: inferrex-mcp-probe

/ what it sends

Unauthenticated, read-only requests.

  • Your robots.txt, read once per host per run, before anything else.
  • An MCP initialize with no credentials and no client capabilities. If the endpoint does not accept the Streamable HTTP transport, the probe tries the older HTTP+SSE transport instead.
  • Public sign-in metadata, when the server answers 401 (or 403 with a sign-in challenge): the OAuth protected resource metadata the challenge points to, and the authorization server's metadata. These requests are GET only.
  • tools/list, when no sign-in is needed, following its pages. If the server opened an MCP session, the probe closes it when it has finished.

/ what it never does

It reads public metadata and nothing else.

  • It never sends a credential and never signs in.
  • It never registers an OAuth client, and never requests an authorization or a token.
  • It never calls a tool, and never reads a resource or a prompt.

/ how politely

How often, and how it paces itself.

  • About once a week per server.
  • One request at a time per host, with a pause of a few seconds between servers on the same host.
  • robots.txt is honoured for the probe's own token, inferrex-mcp-probe, or for * when there is no group for that token. If your MCP endpoint's path is disallowed, the probe skips it.
  • A 429 stops it. The probe sends nothing more to that host for the rest of the run, waits at least as long as Retry-After asks before trying again, and backs off for longer after each further 429.

/ opting out

Two ways to opt out.

In robots.txt, on the host that serves your MCP endpoint:

User-agent: inferrex-mcp-probe
Disallow: /

By email. Write to support@inferrex.com with the host name, and it will be added to the probe's do-not-probe list. A host on that list receives no requests from the probe at all, robots.txt included.