MCP Server - NexRex

This is a separate feature from the Developer API. The Developer API issues organization-scoped keys for building integrations; the MCP Server connects your personal account so an AI assistant can query your own NexRex training data. If you’re building an app or dashboard, see Authentication instead.

The MCP Server (Model Context Protocol, currently in Beta) lets AI assistants such as ChatGPT, Claude, Codex, or Gemini CLI read your NexRex training data directly inside the tool you already work in.

What can the AI assistant access?

Once connected, your AI assistant can:

Read your profile, activities, training plans, nutrition logs, recovery data, and race predictions
Read athletes and groups you coach (if you have coach permissions)
Draft training plans and propose workout adjustments
Analyze performance across single athletes or groups

The AI assistant can propose changes to training plans, but saving or applying changes always requires your explicit approval. No changes are made to your training calendar without your permission.

Connection methods

There are two ways to connect:

Sign in with NexRex (OAuth) — recommended for ChatGPT, Claude.ai, and Claude Code. Add the server URL in your client, which triggers a browser sign-in and approval flow. No token to copy.
Manual token — for Codex, Gemini CLI, or other clients without OAuth support. Generate a token in the web console and paste it into your configuration.

Where does authorization happen? OAuth approval happens in your browser when you add the MCP server in your client (ChatGPT, Claude, etc.). The authorization flow redirects you to NexRex, where you sign in and click Allow access.Settings → Integrations in the NexRex web console is for manual tokens only. You won’t find an “Authorize” or “Allow access” button there — it only generates tokens for clients that don’t support OAuth.

Connect ChatGPT

ChatGPT supports OAuth, so you don’t need to generate a token manually.

Open custom GPTs settings

In ChatGPT, go to your profile settings and select My GPTs or Custom GPTs.

Add MCP server

Click Configure or Add action, then select Add MCP server or similar option. (Note: UI labels may vary as ChatGPT evolves.)

Enter the server URL

Paste https://mcp.nexrex.ai/mcp as the MCP server URL.

ChatGPT opens your browser to the NexRex sign-in page. Sign in with your existing NexRex account.

Approve access

Review the consent screen showing the requesting app’s name and callback address. If the app runs on your own computer, you’ll see a warning about a local return address. Confirm you initiated this connection, then click Allow access.

Start using NexRex in ChatGPT

Once connected, you can ask ChatGPT questions about your training data:

“Show me my recent activities”
“What’s my current training plan?”
“How am I progressing toward my race goal?”

Disconnect from ChatGPT

To remove the connection, delete the MCP server from your ChatGPT custom GPT or profile settings. NexRex will revoke the connection’s tokens automatically.

Connect Claude

Claude.ai (web)

Claude.ai supports OAuth connections similar to ChatGPT.

Open integrations

In Claude.ai, go to Settings → Integrations or Connections.

Add MCP connection

Click Add connection or Add MCP server, then enter https://mcp.nexrex.ai/mcp.

Your browser opens the NexRex sign-in page. Sign in and click Allow access on the consent screen.

Claude Code (CLI)

Claude Code is a command-line tool that also supports OAuth.

Add the MCP server

In your terminal, run:

claude mcp add --transport http nexrex https://mcp.nexrex.ai/mcp

Do NOT use the --header "Authorization: Bearer ..." command shown in Settings → Integrations if you want OAuth. That command uses a manual token and skips the browser authorization flow entirely. For OAuth, use only the command above without any --header flag.

Authorize the connection

Inside Claude Code, run:

/mcp

This opens your browser to authorize the connection. Sign in to NexRex and click Allow access.

Verify the connection

Claude Code will confirm the connection is active. You can now ask questions about your NexRex data.

Disconnect from Claude

Claude.ai: Remove the connection from Settings → Integrations
Claude Code: Run claude mcp remove nexrex in your terminal

Connect Codex

Codex doesn’t support OAuth, so you need to generate a manual token from the NexRex web console.

Generate a token in NexRex

Go to app.nexrex.ai and sign in
Navigate to Settings → Integrations
Find the MCP Server section (marked Beta)
Click Generate token

The full token is shown only once. Copy it immediately — you won’t be able to see it again. If you lose it, you’ll need to regenerate a new token.

Copy the Codex configuration

On the same page, select the Codex tab. Copy the configuration snippet shown:

# ~/.codex/config.toml
[mcp_servers.nexrex]
url = "https://mcp.nexrex.ai/mcp"
http_headers = { "Authorization" = "Bearer YOUR_TOKEN" }

Replace YOUR_TOKEN with the token you just generated.

Update your Codex config

Open or create ~/.codex/config.toml and paste the configuration with your actual token.

Verify the connection

Restart Codex or reload the MCP configuration. Codex should now have access to your NexRex training data.

Use this manual token method when your client doesn’t support OAuth, or when you intentionally want to use a token from Settings → Integrations instead of the browser OAuth flow.

Connect other clients (Gemini CLI, custom tools)

For clients that don’t support OAuth or when you want to use a manual token:

Generate a token in Settings → Integrations

Sign in to app.nexrex.ai
Go to Settings → Integrations
In the MCP Server section, click Generate token
Copy the token immediately (shown only once)

Copy the client-specific config

The web console shows tabs for Claude Code, Codex, and Gemini CLI. Select your client’s tab and copy the configuration snippet. These snippets use manual tokens with the Authorization: Bearer YOUR_TOKEN header.

Add to your client's config

Follow your client’s documentation to add the MCP server URL and token. Most clients use a Bearer token header:

Authorization: Bearer YOUR_TOKEN

Replace YOUR_TOKEN with the token you generated.

Use this manual token method when your client doesn’t support OAuth (like Codex and Gemini CLI), or when you intentionally want to use a token instead of the OAuth browser flow.

Security and tokens

Token lifetime

Each manual token has a creation date and expiry date, shown next to the token’s suffix in Settings → Integrations
There’s no separate revoke action — to invalidate a token immediately, regenerate a new one

Regenerating tokens

When you regenerate a token, a new token is issued. Your previous token keeps working until its expiry date, but the Settings page only tracks the newest one. If you regenerate, update all your AI assistant configurations using the old token.

Best practices

Never commit tokens to version control — treat them like passwords
Don’t share tokens — each token is personal and tied to your NexRex account
Regenerate if compromised — if you accidentally expose a token, regenerate immediately

OAuth security

OAuth connections use PKCE (Proof Key for Code Exchange) and rotating refresh tokens for enhanced security. If NexRex detects reuse of an already-rotated refresh token, the entire connection is revoked and you must reconnect.

Using the MCP connection

Find your own athlete data

The get_current_user tool returns the identity of your connected account:

{
  "user_id": "usr_8f2k...",
  "athlete_id": "usr_8f2k...",
  "email": "you@example.com",
  "display_name": "Jamie Chen",
  "roles": ["coach"],
  "org_id": "org_x1y2...",
  "profile_available": true
}

For coaches: Your own account may not appear in your athlete roster, so roster searches can miss you. Ask your AI assistant to call get_current_user first and use the returned athlete_id to fetch your own profile, training plan, and activities.

Troubleshooting

OAuth clients (ChatGPT, Claude): Remove the connection and reconnect
Manual token clients (Codex, Gemini): Regenerate the token in Settings → Integrations and update your configuration

”Token expired”

Manual tokens have an expiry date. Go to Settings → Integrations and regenerate the token, then update your client configuration.

”Wrong account” or “Can’t see my data”

Make sure you’re signed in to the correct NexRex account when authorizing the OAuth connection, or that your manual token was generated from the right account.

Client doesn’t support OAuth

If your AI assistant doesn’t offer OAuth or you can’t find the MCP connection option, use the manual token method instead. Generate a token in Settings → Integrations and follow your client’s documentation for adding MCP servers with bearer tokens.

​What can the AI assistant access?

​Connection methods

​Connect ChatGPT

​Disconnect from ChatGPT

​Connect Claude

​Claude.ai (web)

​Claude Code (CLI)

​Disconnect from Claude

​Connect Codex

​Connect other clients (Gemini CLI, custom tools)

​Security and tokens

​Token lifetime

​Regenerating tokens

​Best practices

​OAuth security

​Using the MCP connection

​Find your own athlete data

​Troubleshooting

​”Authorization failed” or login loop

​”Token expired”

​”Wrong account” or “Can’t see my data”

​Client doesn’t support OAuth

What can the AI assistant access?

Connection methods

Connect ChatGPT

Disconnect from ChatGPT

Connect Claude

Claude.ai (web)

Claude Code (CLI)

Disconnect from Claude

Connect Codex

Connect other clients (Gemini CLI, custom tools)

Security and tokens

Token lifetime

Regenerating tokens

Best practices

OAuth security

Using the MCP connection

Find your own athlete data

Troubleshooting

”Authorization failed” or login loop

”Token expired”

”Wrong account” or “Can’t see my data”

Client doesn’t support OAuth