API (application programming interface)

What it is

IBM defines an API as a contract that lets software access data or invoke functionality exposed by other software. An API exposes only what’s needed for a specific interaction. Most business software offers web APIs, secured with API keys or OAuth. REST is the dominant style for web APIs.

How it works

1. A client sends a request to an endpoint, such as “create contact”.
2. The server checks the credentials and permissions.
3. It performs the action or returns data, usually as JSON, with a status code that says whether the request worked.

A few terms you’ll meet on vendor docs:

• Endpoint: the address for one action.
• Key or token: proves who’s calling.
• Rate limit: how many calls you can make in a given period.
• Webhook: the reverse direction, where the tool calls you when something happens.

Benefits

• Reliable, fast and auditable automation.
• The foundation for webhooks, MCP servers and integrations.
• IonBin’s tool pages mark which tools have an official API.

Limits and risks

• API keys are secrets. Store them safely, scope them narrowly and rotate them.
• Plans often limit API access or call volume (see rate limits).
• APIs change versions, so integrations need maintenance.
• If a tool has no API, you may need browser automation, which is slower and breaks more easily.