# X_MCP_HOST_REFUSED

## Means

an MCP request named a Host that is not this machine

## Typical cause

x mcp serve answered a request whose Host is not localhost, a *.localhost name or a loopback address — the shape of a DNS-rebinding page, whose Host and Origin agree. Answered 421 before the bearer token is read

## Fix

`curl -X POST http://localhost:9229/mcp -H 'authorization: Bearer <token>'`

[MCP and AI](/error-codes#mcp-and-ai)