What It Actually Means
The everyday version is that it is how your systems can share information without a person copying it between them. Your website sends an enquiry to your CRM. Your invoicing system pulls hours from your time tracking. Your stock updates your online shop.
Why It Is A Buying Question
This is the reason to understand it at all. The presence and quality of an API decides whether a product can ever be part of a connected operation, or will always be an island.
That question is worth asking before you buy anything, and it is asked far too rarely. Software is chosen on features, and the constraint that bites two years later is that it will not talk to anything.
The pattern is familiar. Each tool works well. Between them, someone exports a spreadsheet every week and types the results into the next system. The cost is not the licence fee. It is a permanent tax in staff time and a permanent source of errors, and it exists because nobody asked at the point of purchase.
What Separates A Good One From A Nominal One
Plenty of products claim to have an API. The differences that matter:
Coverage. Can it do what the interface does, or only a fraction? Read-only APIs are common and severely limiting, because most useful automation involves writing something back.
Documentation. Good documentation makes integration a known quantity. Poor documentation means paying a developer to work it out by experiment, and that is where integration budgets are lost.
Rate limits. How many requests are permitted. Restrictive limits can make an otherwise viable integration impractical.
Stability. Whether the vendor changes it without warning. A provider that breaks its API regularly imposes a recurring maintenance cost you did not agree to.
Cost. Some vendors put API access on a higher tier. That is a legitimate charge and it belongs in the comparison, because it can double the real price.
What To Ask Before Buying Anything
- Does it have an API, and does it cover what we need to automate? Not just whether one exists.
- Is API access included in this price?
- Can we get our data out through it, in full? This is also your exit route. A product you cannot extract from is one you cannot leave.
- How often does it change, and how much notice is given?
- Are there existing integrations with the other things we use? Frequently cheaper than building.
The Related Thing Worth Knowing
An API is something you ask. A webhook is something that tells you, pushing a message when an event happens rather than waiting to be asked.
Most well-connected setups use both: webhooks so things happen immediately when they occur, and API calls to fetch detail or catch anything missed. A product with an API and no webhooks can be integrated, and it will always be slightly behind, because something has to keep asking.
Whether this all works in practice is integration work rather than a feature you buy, and the quality of the APIs involved decides how much of it there is.
More terms are in the glossary.
