Install the MCP server

Claude Desktop

Edit claude_desktop_config.json (location: Settings → Developer → Edit Config) and add:

{
  "mcpServers": {
    "42a": {
      "command": "npx",
      "args": ["-y", "@42a/mcp@latest"],
      "env": {
        "API_42A_KEY": "ck_live_..."
      }
    }
  }
}

For a user key that should target a specific org, also set API_42A_ORG_ID:

"env": {
  "API_42A_KEY": "ck_live_...",
  "API_42A_ORG_ID": "org_2abcde"
}

Restart Claude Desktop. The 42A tools should appear in the tool picker.

Claude Code

Add to your project's .mcp.json:

{
  "mcpServers": {
    "42a": {
      "command": "npx",
      "args": ["-y", "@42a/mcp@latest"],
      "env": { "API_42A_KEY": "ck_live_..." }
    }
  }
}

Verify

Ask Claude:

"List my 42A projects and tell me which is the most recently updated."

You should see a list_projects tool call in the conversation, followed by Claude's summary.

Troubleshooting

• "API_42A_KEY environment variable is required" - the key wasn't set in the MCP config's env. Confirm you saved the JSON file and restarted the client.
• "42A API 401" on every call - the key is invalid or revoked. Generate a fresh one in Settings → API keys.
• "X-Org-Id header is required" - you're using a user key but didn't set API_42A_ORG_ID. List your accessible orgs with list_organizations, then add the chosen org_xxx to the env.

Last updated May 3, 2026