Using IcuSync with Grok and ChatGPT for Intervals.icu
Using IcuSync

Using IcuSync with Grok and ChatGPT for Intervals.icu

Aug 17, 2026·2 min read
Toby Pattullo

By Toby Pattullo

Australian Deaflympic marathon and ultra runner, and the solo developer behind IcuSync.

IcuSync is built for Claude, and works on Claude's free plan with one custom connector, no paid subscription needed. Because it uses MCP (Model Context Protocol), an open standard, it also works with other AI assistants that support the protocol. Grok added Bring Your Own MCP support in May 2026, and it works on Grok's free plan.

How to Connect IcuSync to Grok

  1. Go to grok.com/connectors
  2. Click New Connector
  3. Select Custom
  4. Paste your IcuSync MCP URL (includes your token, no separate authentication needed)

Once connected, IcuSync is available across Grok web, iOS, and Android. Setup takes a couple of minutes and no separate mobile setup is needed once it's added on grok.com.

Grok can read your training data, build workouts, and push them to your Intervals.icu calendar the same way Claude does.

How to Connect IcuSync to ChatGPT

ChatGPT's support for custom MCP apps depends on your plan. Business and Enterprise/Edu admins can enable Developer Mode and create custom MCP apps. Plus and Pro users can enable Developer Mode themselves. Free accounts don't currently support custom MCP apps.

Setup is done on the ChatGPT web app. Custom MCP apps are not currently available on ChatGPT mobile.

Note on ChatGPT Go: ChatGPT Go is a separate lower cost plan, not the same as the free plan. Custom MCP apps aren't available on Go either, only Plus and higher support Developer Mode. If you're on Go, you can still use IcuSync for free on Claude instead, no paid plan needed.

  1. Go to chatgpt.com on the web browser
  2. Go to Settings → Apps → Advanced Settings and enable Developer Mode, if available
  3. Create a custom app
  4. Paste your full IcuSync MCP URL from your IcuSync dashboard. Use the long URL that includes your token, not just https://mcp.icusync.icu/mcp
  5. Set Authentication to No authentication. Don't choose OAuth, because your token is already in the URL
  6. Save, and IcuSync connects straight away with no sign-in page

Seeing an "Invalid redirect URI" error? It means ChatGPT is trying OAuth sign-in. Delete the app, create it again with your full MCP URL, and set Authentication to No authentication.

ChatGPT's connector setup has changed a few times this year, so steps may shift. Accurate as of September 2026.

Read the full breakdown in our honest comparison with ChatGPT.

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