Notion MCP 401 in n8n/Docker: {"code":"unauthorized","message":"API token is invalid."} with tools list working

Notion MCP 401 in n8n/Docker: {"code":"unauthorized","message":"API token is invalid."} with tools list working

TL;DR: Your OPENAPIMCPHEADERS env value is misquoted, so the Authorization header never reaches the server even though tools list works. Escape the inner quotes: OPENAPIMCPHEADERS as a JSON string with backslash-escaped quotes. Restart the n8n container so the corrected env takes effect.

The error

{"status":401,"object":"error","code":"unauthorized","message":"API token is invalid."}

Fix it

1. Inspect the OPENAPIMCPHEADERS value in your docker-compose file or n8n env. Expected: The quotes around the JSON are unescaped or the value is split.

2. Set it as a single properly escaped string, e.g. OPENAPIMCPHEADERS with escaped inner quotes around Authorization and Notion-Version. Expected: The value parses as valid JSON with both headers.

3. Restart the container. Expected: Tool calls authenticate and return data.

When this applies

Notion MCP tools/list succeeds but every tool call 401s with unauthorized/API token is invalid, in n8n or Docker Compose.

When this does NOT apply

If tools/list also fails, the token or URL is wrong. If the token fails in curl, regenerate it.

Tool compatibility

makenotion/notion-mcp-server via n8n or Docker Compose

Also seen as

• notion MCP n8n API token is invalid
• OPENAPIMCPHEADERS 401
• notion MCP docker unauthorized tool calls

Why it happens

tools/list does not need the Notion credential, but every tool call does. A misquoted OPENAPIMCPHEADERS means the server never forwards the Authorization header, so Notion 401s each call while listing tools works fine.

Edge cases

• YAML quoting rules differ between compose file styles; test with a JSON parse.
• n8n community packages need N8NCOMMUNITYPACKAGESALLOWTOOL_USAGE=true for tool use at all.
• Restarting the container matters; compose does not re-read env on its own.

Documented in nerding-io/n8n-nodes-mcp issue #90, where tools list worked, calls 401d, and escaping the quotes in OPENAPIMCPHEADERS fixed it. https://github.com/nerding-io/n8n-nodes-mcp/issues/90