API integration checklist: questions before implementation

Prepare an integration contract covering identifiers, credentials, limits, retries, test data, reconciliation and ownership before development begins.

A central integration hub connected to separate systems through silver channels.

A Swagger file describes request and response shapes, but it rarely explains the complete operating agreement between two businesses. Before development begins, establish who owns each data field, what an accepted response means and how the integration recovers from uncertainty. Write the answers beside the API contract. This prevents developers from silently inventing rules for duplicates, missing data or delayed notifications.

Confirm access and environment boundaries

Record the provider, API version, base URLs, authentication method and credential owner. Keep production and test credentials separate. Check available permissions and whether access can be limited to the required operations. Identify test records that can be safely created or changed. Document rate limits and the provider’s instructions for handling them. A successful authentication request does not prove that every required business operation is available.

Define the data agreement

Choose stable identifiers for both systems and retain their mapping. For each field, specify type, required status, timezone or currency semantics, null handling and ownership. Decide how deletes and corrections propagate. If both systems can edit an address, determine whether one wins, a version check rejects conflicts or an operator resolves them. These decisions belong to the product and data owners, not to an incidental timestamp comparison.

Agree failure and recovery behaviour

Define connection and response timeouts, bounded retries and which operations can be repeated safely.
Confirm how duplicated or reordered notifications are detected and how processing results are retained.
Design a reconciliation check that can discover missing changes independently of the event stream.
Name the owner of rejected records and provide enough redacted evidence to diagnose the cause.

Make acceptance observable

Create test cases for success, invalid data, expired credentials, throttling, remote outage and partial completion. Test the same business operation twice and after an interruption. Record expected states in both systems, not just HTTP codes. Agree release sequencing, monitoring, escalation and the notice period for provider changes. The completed checklist should produce an implementation-ready contract and a list of unresolved dependencies. If an answer is unknown, keep it visible with an owner rather than treating a blank field as an implicit approval to guess.

Frequently asked questions

Is OpenAPI enough to start?

It helps with syntax, but ownership, recovery, limits and business acceptance still need explicit decisions.

Should we log full requests?

Log only the evidence needed, with credentials and sensitive fields removed and an appropriate retention policy.

What does a successful response prove?

Only the documented response semantics. Acknowledgement may precede final processing or downstream delivery.

Who handles rejected records?

Assign a named operational owner and a repair process, rather than leaving records in an unmonitored queue.

Do we need reconciliation with webhooks?

Often yes. An independent comparison can detect gaps that a missed or failed notification would not reveal.

Bring the scope. We will help make it buildable.

Share the user journey, integrations and launch constraints. We can clarify the scope and prepare an estimate with assumptions and exclusions.

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