Developers and AI assistants
One operation registry produces the REST route, the MCP tool and the OpenAPI document, so what a script can do and what an assistant can do never drift apart.
REST v1
API keys with a closed scope grammar (invoices:read, invoices:write, …), per-key rate limits, idempotent writes, an audit record for every call.
OAuth 2.1
PKCE, discovery, dynamic client registration and a consent screen that shows exactly which scopes an app asks for. Step-up for write scopes.
MCP server
Connect ChatGPT, Claude or Gemini to a workspace at https://api.billingmart.com/mcp. Tools read, draft and propose; nothing sends or moves money without a person approving it in the console.
What a connected assistant can do, with the steps to connect one. The OpenAPI document and the console’s API keys page are the reference for everything else.