API Development for Your Business

What an API buys you

• Your systems exchange data without anyone re-typing it
• Partners and customers integrate without your involvement
• A mobile app becomes possible without rebuilding the backend
• Automation has something reliable to call
• Replacing one system later becomes feasible, because the interface is defined

That last one is underrated. Systems with clean interfaces can be replaced piece by piece; systems without them get replaced all at once, which is how businesses end up betting a year on a migration.

What makes one good

1. Predictable. The same patterns everywhere — naming, pagination, filtering, errors.
2. Documented with examples. A developer should make a successful call in under ten minutes.
3. Versioned. Changes must not break existing consumers, ever.
4. Honest errors. Status codes that mean what they say and messages that explain what to do.
5. Authenticated properly. Per-consumer keys, scoped permissions, revocable.
6. Rate limited. Protects you and tells consumers the limit before they hit it.

The test of an API is whether a developer who has never met you can integrate with it using only the documentation. If they need a call, the documentation is the deliverable that is missing.

Design mistakes we are asked to fix

• Endpoints mirroring the database instead of the business — consumers reassemble your schema to do anything
• Everything returning 200, including failures, with the real status in the body
• No pagination, so a large account times out
• Breaking changes without a version, silently, on a Tuesday
• Bespoke authentication rather than a standard scheme
• Documentation generated from code with no examples

Internal and external are different products

An internal API can change with a message in a channel. An external one is a contract with people you cannot coordinate with, and it needs versioning, deprecation notices and a support route.

Businesses get into trouble by exposing an internal API to partners without upgrading it to that standard. The first breaking change teaches everyone the difference, expensively.

What it costs

The gap between the first and second rows is mostly documentation, key management, rate limiting and support tooling — none of which is glamorous and all of which decides whether anyone can use it.

Where to start

With the integration you already need. Do not design a comprehensive API in the abstract; build the endpoints one real consumer requires, learn from that, and extend.

APIs designed without a consumer are consistently wrong in the same way: they expose what was easy rather than what was needed, and the first real integration rewrites half of them.

Frequently asked questions