Error 401 status sending message to https://mcp.notion.com/sse: {"error":"invalid_token"}

Error 401 status sending message to https://mcp.notion.com/sse: {"error":"invalid_token"}

TL;DR: Use the /mcp endpoint, not /sse; the SSE path is deprecated and rejects the token. Update the server URL in your MCP config to https://mcp.notion.com/mcp. Reconnect; the OAuth handshake completes on the supported path.

The error

Error 401 status sending message to https://mcp.notion.com/sse: {"error":"invalid_token","error_description":"The access token is invalid or has expired."}

Fix it

1. Open your MCP config and find the Notion remote server URL. Expected: It points at https://mcp.notion.com/sse.

2. Change the URL to https://mcp.notion.com/mcp. Expected: The config uses the /mcp path.

3. Reconnect the server. Expected: OAuth completes and tools list loads without 401.

When this applies

The hosted Notion MCP server 401s with invalid_token specifically on the /sse URL.

When this does NOT apply

Local stdio servers do not use this URL at all. A bad local token is the Claude Code env issue.

Tool compatibility

Notion hosted MCP (mcp.notion.com), remote clients

Also seen as

• notion MCP sse invalid_token
• mcp.notion.com 401
• notion remote MCP endpoint deprecated

Why it happens

Notion moved the hosted MCP endpoint from /sse to /mcp. The old path no longer accepts tokens, so every request 401s with invalid_token even when the OAuth grant is fine.

Edge cases

• Some setup guides still show the /sse URL; check the date on the guide.
• After switching, clear the stored OAuth grant once.
• The /mcp path uses Streamable HTTP; older clients may need an update.

Documented in community reports on the Notion hosted MCP, where the /sse URL returned invalid_token and switching to /mcp fixed it. https://github.com/makenotion/notion-mcp-server