IntervalSync
Secure connection portal
MCP server · ChatGPT

Intervals.icu
in ChatGPT.

IntervalSync is a hosted MCP server for Intervals.icu. Add its address to ChatGPT once, sign in with your Intervals.icu account, and ChatGPT can read your activities, intervals, per-second streams, wellness and planned workouts when you ask about them.

There is no API key to paste into ChatGPT and nothing to install. ChatGPT gets a short-lived, revocable token for your training connection, and never sees your Intervals.icu credential.

Before you start

Which ChatGPT plan you need.

ChatGPT decides by plan what a custom MCP server can do. As of 14 October 2026, OpenAI's page on connecting custom MCP servers says:

ChatGPT planRead your trainingWrite planned workouts and wellness
BusinessYes. Only the workspace's admins and owners can add a custom MCP server.Yes: Business has full MCP, which includes write actions.
Enterprise and EduYes. Admins and owners can add one, and can give other members the permission to.Yes: full MCP. Admins can also turn single actions off.
ProYes. OpenAI says Pro users can connect custom MCP servers with read and fetch permissions.No: full MCP is for Business, Enterprise and Edu.
Plus, Go and FreeOpenAI's page does not list them.No.

A custom MCP server is added on ChatGPT on the web; OpenAI says it cannot be connected from the mobile apps. OpenAI changes these rules, so read their page for where they stand before you rely on this one, and before you pay for anything.

IntervalSync has plans of its own too. Reading works on every plan, and writing needs the 14-day trial, Pro or a Coach plan: pricing has each one, and the terms set out the rules.

Step by step

Add IntervalSync to ChatGPT.

These are the steps in ChatGPT's Plugins, as OpenAI describes them on 14 October 2026. On Business, Enterprise and Edu, a workspace admin or owner adds the server, or a member they have given permission to.

  1. In ChatGPT on the web, open Plugins.
  2. Select the plus button, then Add custom MCP server.
  3. Name it IntervalSync. The description is optional.
  4. Under Connection, enter the server URL: https://intervalsync.icu/mcp/v2
  5. For authentication, choose OAuth and leave any client ID and secret empty.
  6. Read the risk warning, select I understand and want to continue, then Create as a plugin.
  7. Complete the IntervalSync sign-in with your Intervals.icu account when ChatGPT opens it.
  8. Review the tools ChatGPT found, and install the plugin.
  9. Start a new conversation, type @, select IntervalSync, and ask: List my last three activities.

If your ChatGPT still shows the older settings rather than Plugins, the path is the one in the guide in your IntervalSync portal: turn on developer mode in ChatGPT's connector settings (on a Business, Enterprise or Edu workspace an admin enables it under Permissions & Roles), add a custom connector with the server URL, acknowledge the custom-server warning, and complete the IntervalSync sign-in.

Writes

Nothing changes until you confirm it.

Four IntervalSync tools change your Intervals.icu data: they create, update and delete planned workouts, and update wellness records. Each one shows you the exact change before it is made, and nothing else on the workout is touched. ChatGPT may also ask before it uses a tool, depending on the app permissions you set in ChatGPT.

A write needs two things: a ChatGPT plan with full MCP, and IntervalSync's trial, Pro or a Coach plan. Reading your training needs neither.

If it does not work

The common fixes.

ChatGPT says IntervalSync is connected, but does not use it.

OpenAI says choosing an app applies to the message you choose it in. Type @ and select IntervalSync in the message that needs your training, or start a new conversation and select it there.

New IntervalSync tools do not appear in a Business or Enterprise workspace.

OpenAI says a workspace keeps the list of tools it approved, and a server's later changes are not applied until an admin refreshes the tool list from the workspace's app settings.

A tool says a permission is missing.

Intervals.icu lets you choose which permissions to grant. Open IntervalSync, select Settings, go to AI Vendor Connections and choose Refresh Intervals permissions if it is shown, or sign out and sign back in, and approve the one that was left out. Do not paste an API key into ChatGPT.

A tool says a daily limit was reached.

Every IntervalSync plan has a daily limit on calls to Intervals.icu, and the message says when the count starts again. The terms set out each one.

Still stuck? Support has the rest, and a form that reaches the people who build IntervalSync.

Next

Once it is connected.

Ask about a date range and a decision rather than "how is my training?". The prompt library has questions that work, and questions with no chart shows what an assistant can answer that Intervals.icu has the data for but no chart.

The Intervals.icu MCP server · Support · Connect your training