No CORS headers

no-cors · CORS & headers

Endpoint (Streamable HTTP)

https://chaos-mcp.thomascdnns.com/s/no-cors/mcp

On the wire — recorded from a real request

Symptom

what you'll observe

Browser-based clients fail with a CORS error; curl/CLI clients work fine.

Cause

what this reproduces

Server never sets Access-Control-Allow-* headers and rejects the preflight.

Fix

how you'd resolve it

Set Access-Control-Allow-Origin and friends; answer OPTIONS preflight with 204.

Try it with curl

bash

curl -sS -X POST \
  https://chaos-mcp.thomascdnns.com/s/no-cors/mcp \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json' \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "initialize",
    "params": {
      "protocolVersion": "2024-11-05",
      "capabilities": {},
      "clientInfo": {"name": "curl", "version": "1"}
    }
  }'