Does the Plain MCP server support API key authentication?
No. The Plain Model Context Protocol (MCP) server at https://mcp.plain.com/mcp supports OAuth only.
How authentication works
You authenticate with your existing Plain account through OAuth. The MCP session inherits your permissions, and replies and actions appear under your user, as in the app. This ties MCP activity to a real user for audit and attribution.
Each person who uses the server needs a Plain account with any role, including Viewer, and must complete the OAuth flow once in their MCP client, such as Cursor, Claude or ChatGPT. There is no shared credential that lets several engineers connect.
Use a custom MCP server with a machine user API key
To give a team of engineers access to Plain data without individual Viewer accounts, build a lightweight custom MCP server that wraps Plain's GraphQL API with a single machine user API key.
- In Settings, open Machine Users and create a machine user with read-only permissions.
- Generate an API key for that machine user.
- Build an MCP server that uses the key to call Plain's GraphQL API and exposes the tools your team needs.
- Point your engineers' MCP clients at your custom server.
The trade-off is that all activity goes through the machine user, so there is no per-engineer attribution in your workspace timeline.