An SLA states a commitment about reliability — availability, latency, and what happens when you miss — and it is one of the clearest signals that an API operation is serious about the businesses building on it. For a consumer it is the difference between a dependency they can plan around and a gamble they are quietly taking.
Start with an SLO you measure honestly for a few months before you turn it into a contractual SLA. A published number you cannot hit is worse than no number. Define precisely what counts: which operations, measured from where, excluding what, over what window, with what remedy.
Do not forget the support half. An availability percentage with no response-time commitment is only half a promise — consumers care as much about how quickly a human engages when something is wrong as about the uptime figure.
And publish it in a machine-readable form alongside your plans, so it can be compared, catalogued, and checked rather than living in a PDF somebody has to request. Making the commitment legible is part of making it real.
