OneMCP documentation

Claude Desktop / Claude Code

// ~/Library/Application Support/Claude/claude_desktop_config.json
{
  "mcpServers": {
    "onemcp": {
      "command": "npx",
      "args": ["-y", "@altura_ma/onemcp"]
    }
  }
}

Hosted mode (API key)

{
  "mcpServers": {
    "onemcp": {
      "url": "https://api.onemcp.fr/mcp",
      "headers": { "Authorization": "Bearer mk_live_xxx" }
    }
  }
}

1. Get an API key

Sign up at onemcp.fr/#signup — 1,000 free calls/month, no credit card. Keep the key shown (it will not be visible again).

2. Import the spec into GPT Builder

In ChatGPT → Explore GPTs → Create → Configure → Actions → Import from URL, paste:

https://api.onemcp.fr/openapi-gpt.json

Auth: API Key, header name Authorization, value Bearer mk_live_xxx.

3. Add the system instructions

You have access to OneMCP via the call_onemcp_tool action.
Use it for any query about French companies,
addresses, public procurement, real estate, EU VAT, or patents.
Parameter: {"tool":"company_search","params":{"query":"..."}}

Native Lemlist & Apollo.io tools

Add the connector, and tools appear automatically in tools/list, namespaced <connector>__<tool>.

Any REST API

Any connector with a base_url (catalogue or custom) exposes a generic tool <connector>__http_request — method, path, query, body of your choosing. Ideal for a service with no dedicated native tools (HubSpot, Airtable, Stripe, Brevo, Slack, Notion, GitHub, Linear, Firecrawl, Apify…).

Universal MCP proxy

Register the URL of an already-hosted third-party MCP server (Notion, GitHub Copilot, Apollo, Stripe, Linear…) — its tools are merged into your /mcp, namespaced and cached for 5 minutes.

OAuth2 — 1-click connection

Some connectors (e.g. Google Drive) use OneMCP's OAuth app — click "Connect", authorize, done. For others, bring your own OAuth2 app (client_id/secret) via the custom connector form.

OAuth2 on /mcp (ChatGPT Apps, Codex)

In addition to mk_live_..., /mcp accepts standard OAuth2 authentication (RFC 7591/8414) — required for the OpenAI Apps portal's "OAuth" mode. Both modes work in parallel, no migration needed for your existing keys.