ChatGPT¶

Web and desktop¶

ChatGPT connects over MCP in Developer mode, using OAuth.

In Settings → Apps & Connectors → Advanced settings, turn on Developer mode.
Back in Apps & Connectors, click Create.
Enter a name, the URL https://trilium-mcp.example.com/mcp and authentication OAuth, confirm that you trust the server, and create it.
The trilium-mcp login page opens; enter your Trilium password.
In a chat, pick the connector from the Developer mode menu to use its tools.

Android¶

The Android app doesn't support MCP yet, but it can use a Custom GPT's Actions, which are plain REST calls. With CHATGPT_ACTIONS=true (and MCP_BASE_URL set to the public HTTPS URL), the server also serves:

GET /chatgpt/openapi.json: the ETAPI spec trimmed to the 30 operations a GPT Action allows (no login/logout, ZIP import/export or attachments), pointed at the proxy below. It's public, like the ETAPI spec itself.
/chatgpt/etapi/...: a REST proxy to Trilium that forwards only those 30 operations, with the same token handling as MCP calls. Trilium itself can stay private.

Set up the Custom GPT¶

On chatgpt.com, open Explore GPTs → Create → Configure → Create new action.
Choose Import from URL and enter https://trilium-mcp.example.com/chatgpt/openapi.json.
Under Authentication, choose API Key with auth type Bearer, and paste an ETAPI token. Raw ETAPI tokens need the token or both auth mode.
Save the GPT as Only me. It then shows up in the Android app.

A stopgap

OpenAI is retiring custom GPTs (from Dec 11, 2026 for Enterprise workspaces; other plans may follow). Treat this as a bridge until ChatGPT's mobile apps support MCP. The reasoning behind it is in the design decision.