ChatGPT and Marrow
Cloud MCP
ChatGPT reads your Marrow data through a custom MCP server you add once on chatgpt.com. On Free and Plus, Codex CLI is the way in.
Open in Marrow works on an iPhone with Marrow 1.6 or later.
OpenAI lets Pro accounts read from custom servers but not write, so on Pro ChatGPT can answer but not log. Business and Enterprise get both.
Custom servers are added on chatgpt.com in a browser. The phone apps cannot add one.
Cloud MCP (Custom MCP server) Pro
A private copy of your data on Marrow's server. Your AI reads it any time, phone asleep, and every sign-in is approved on your phone. You need: ChatGPT Pro, Business, Enterprise or Edu, on the web.
- In Marrow, open Connects, then AI, and tap ChatGPT. Pick Cloud MCP.
- Turn Cloud MCP on (Marrow Pro) and add ChatGPT to Your AIs. Marrow shows your link.
- On a computer, open chatgpt.com/plugins.
- Select +, then Add custom MCP server.
- Server URL: your link. Authentication: OAuth.
https://connect.marrowhealthapp.com/t/<your-id>/mcp - Type the code the page shows into Marrow and approve.
- In a chat, type @ and pick Marrow.
- Ask: How am I doing today?
Placeholder shown: Marrow fills in your own link.
What it can do
- Read. A daily brief scored against your own normal, your baselines, what changed this week, any metric day by day, workouts, lifts set by set, sleep stages and your food diary.
- Log. On Business and Enterprise, ChatGPT can log meals, workouts and more after you turn on Allow AI write. On Pro it reads only.
Try asking
- How am I doing today?
- What changed in my sleep this week compared with my normal?
- Which of my lifts went up this month?
- Log a turkey sandwich and an apple for lunch.
If it does not work
In ChatGPT
- No + on chatgpt.com/plugins, or Not available on your plan. OpenAI offers custom MCP servers on ChatGPT Pro, Business, Enterprise and Edu, on chatgpt.com in a browser. The phone apps cannot add one. On other plans, Codex CLI is the way in.
- Admin approval required, Disabled by admin, or Requires workspace setup. In a Business or Enterprise workspace, only admins and owners add custom servers. An admin grants the Create plugins with MCPs permission in Workspace settings, Permissions and roles.
- No Developer mode in Settings. OpenAI no longer requires it for this. Go to chatgpt.com/plugins, select +, then Add custom MCP server.
- Connected, yet ChatGPT does not use it. Type @ in the chat and pick Marrow. An app can show as Connected and still be unavailable for the model or the surface you are in.
- A Local MCP or Server MCP address does not work. ChatGPT connects from OpenAI's servers and signs in with OAuth only. It cannot send a token, so it takes the Cloud MCP link.
- The tool list is out of date. Open the connection on chatgpt.com/plugins and select Refresh.
Cloud MCP checks
- The sign-in waits in Marrow. The sign-in page shows a 6-character code. Open Marrow, go to Export, type the code and tap Approve. A request expires after ten minutes and three wrong codes deny it. If that happens, start again from your AI.
- The page says the link did not match a Marrow. In Marrow, open your AI under Connections, tap Copy your link and paste the whole link.
- It worked, then stopped. When Cloud MCP is off, or Marrow Pro has ended, the copy is paused. Switching Cloud MCP off also signs every AI out. Turn it back on, switch this connection on in Your AIs and sign in again from your AI.
- Approve stops at the limit. Each AI is one connection. Free keeps 3 connections on at a time. Marrow Pro keeps up to 20: AIs, servers and automations together. Sources never count. Turn one off in Your AIs or Your Exports, then approve again.
- It reads but cannot log. Turn on Allow AI write for Cloud MCP in Marrow. An entry reaches the phone within seconds when notifications are allowed for Marrow, or the next time you open the app.
More fixes in the guides: Cloud MCP.
