An API is a promise to unknown consumers about how your system behaves. Once published, that promise is difficult to change without breaking trust.
That’s why API design deserves far more care than it usually receives.
Good APIs are boring in the best way. They are predictable, explicit, and unsurprising. They avoid clever shortcuts in favor of clarity. Consumers should not need to guess what an endpoint does or how a field behaves under edge conditions.
One of the hardest parts of API design is restraint. Every field added is a commitment. Every optional parameter increases the surface area for bugs. Flexibility feels generous in the moment but becomes expensive over time. Strong APIs say “no” more often than “yes.”
Consistency matters more than perfection. Naming conventions, error formats, pagination strategies—these things compound. Inconsistent APIs force consumers to write special-case logic, which is a hidden tax on every integration.
