What is an API?
An API, or application programming interface, is a set of rules that lets one piece of software ask another to do something, such as send a message or list your conversations.
Also called: Application programming interface.
In plain words
People use apps through screens and buttons. Software uses other software through an API. Instead of tapping "send", a program sends a short request to the service's API saying what to send and to whom, and the service answers whether it worked.
APIs are why your booking system can email you when someone books, or why your shop can update your accounting software on its own. Each request usually carries a key that proves which customer it comes from, so the service knows whose account to act on.
You do not need to read an API to benefit from one. AI agents and other tools use APIs behind the scenes, and MCP is a newer standard that makes APIs easier for AI agents in particular to use.
When people talk about the "WhatsApp API" or the "Instagram API", they can mean different things: the platform's own developer programme, or a service like Spaces that offers its own API for working with accounts you connect. It is worth asking which one a tool uses, because the rules differ.
How it works in Spaces
Spaces has a REST API and an MCP server that do the same things: list chats, read messages, reply, start a chat, schedule a message, set up routines and more. Most owners never touch the API directly, because their AI agent uses the MCP server.
Every send through the API follows the same safety limits as a send from an agent, a scheduled message or a routine. Developer detail lives in the docs.
Related terms
- API key: An API key is a long secret code that proves to a service that a request comes from you, so it works like a password for software rather than for people.
- MCP: MCP, the Model Context Protocol, is an open standard that lets an AI agent connect to an outside service and use its tools, a bit like a universal plug between AI apps and the services they work with.
- Webhook: A webhook is a message one service sends automatically to another's web address the moment something happens, such as a new customer message arriving.
- MCP server: An MCP server is the web address a service publishes so AI agents can find and use its tools through the Model Context Protocol.
FAQ
Do I need to know how to code to use Spaces?
No. Most owners connect their AI agent through the MCP server and talk to it in plain words. The API is there for developers who want it.
What is the difference between an API and MCP?
An API is the general way software talks to a service. MCP is a standard way for AI agents to discover and use a service's tools.
Does Spaces use WhatsApp's developer platform?
No. Spaces connects your own WhatsApp number by QR code. It does not go through the WhatsApp Business Platform.
Does the API follow the same limits as my agent?
Yes. Every send, from any route, uses the same per-account limits.
Where is the API documented?
In the Spaces docs, with the full list of routes and what each refusal means.
Useful next: Developer docs, WhatsApp API, Instagram API, LinkedIn API. Every term: the glossary.