An API integration checklist for before you write code

Start with the business event

“Connect system A to system B” is not yet a scope. Name the event that starts the work, the record that should change, the allowed delay, and the person who owns the result. A new paid order becoming a fulfillment request is clearer than “sync orders.”

Write down which system is authoritative for each important field. Without that decision, a two-way sync can turn a small disagreement into an endless loop of overwrites.

Inspect the real interfaces

Documentation is a starting point. Discovery should also confirm account tier, API version, authentication method, sandbox quality, rate limits, pagination, webhook availability, and the fields available in the actual tenant.

Ask who can create credentials, how secrets will be rotated, and what happens when a user leaves. An integration that depends on one employee’s personal token already has an operational defect.

• Sample payloads from the real systems, with sensitive data removed.
• Field definitions, required values, and ownership rules.
• Expected volume, bursts, backfills, and rate limits.
• Timeout, retry, duplicate, and partial-failure behavior.
• Logging access, alert ownership, and recovery procedure.

Find the exceptions early

The happy path is usually the shortest part of an integration. Ask what happens when a customer has no email address, two records match, a required option was deleted, or the destination is unavailable for an hour.

Not every exception should be automated. Some should stop safely and enter a review queue with enough context for a person to decide.

Turn discovery into acceptance tests

A useful scope names observable results: one destination record per source event, required fields mapped correctly, duplicates suppressed, failed events visible within a stated time, and replay proven in a test environment.

Those tests create a shared finish line. They also expose missing decisions before they become change requests in the middle of implementation.