Qdrant MCP: QDRANT_URL on gRPC port 6334 (use REST port 6333)

TL;DR: Qdrant has two ports: 6333 for REST, 6334 for gRPC. The MCP server speaks REST. If QDRANT_URL uses 6334, switch it to 6333.

Connection failed / unexpected response from Qdrant

(With QDRANT_URL set to the service URL for that host and port.)

Fix it

1. Check the port in your client config env block:

{
  "env": {
    "QDRANT_URL": "http://YOUR_QDRANT_HOST:6334"
  }
}

1. Change 6334 to 6333:

{
  "env": {
    "QDRANT_URL": "http://YOUR_QDRANT_HOST:6333"
  }
}

1. Sanity-check with curl:

curl http://YOUR_QDRANT_HOST:6333/collections

Expected: JSON listing collections.

1. Restart the MCP client.

Expected: the server connects.

When to use this

• QDRANT_URL contains port 6334 and the server cannot talk to Qdrant.
• The curl check against 6333 works but the server is configured for 6334.

When NOT to use this

• The URL already uses 6333 and still fails. Then it is a host, auth, or Qdrant-down problem.
• The error is 401. Auth, not ports.

Compatibility

• qdrant/mcp-server-qdrant and REST-based Qdrant MCP servers.

Why it happens

Qdrant's Docker image publishes both ports side by side, and docs mention them together, so it is easy to grab the wrong one. gRPC speaks HTTP/2 with a binary protocol; a REST client opening a conversation there gets nothing it understands.

Edge cases

• Qdrant Cloud URLs include the port explicitly (:6333). Keep it.
• If you run Qdrant behind a reverse proxy, the external port may differ from 6333. Use whatever port serves the REST API externally.
• Some setups only map 6333 in Docker. Then 6334 is unreachable from outside the container entirely.