Back to Sumline
API Access

Free Sumline API key

Call Sumline's calculators from ChatGPT, Claude, Cursor, or any HTTP client via our MCP endpoint. Free tier: 5 calls per day. No credit card required.

We'll send your key to this address so you have a backup copy.

Need more calls? Upgrade to Pro for unlimited access from your account.

How to use your key

Send it as the x-api-key header to https://usesumline.com/mcp. Any MCP-compatible client (ChatGPT, Claude Desktop, Cursor) can be pointed at that URL.