Agree on what the data actually means
A field with the same name in two systems may mean different things. Agree on identifiers, statuses, currencies, time zones and which side is authoritative for each value. Define record creation, updates and deletion where relevant. This prevents errors that a successful server response does not reveal. Real sample data and documentation from both systems are useful starting points, rather than a product page simply claiming that an API is available.
A retry should not create a second order
A connection can fail after an action succeeds but before the sender receives confirmation. Plan operation identifiers, retries and ways to check the outcome. Not every error should be retried forever; some need corrected data or staff attention. Important events need a log with understandable states. This work is less visible than a new button, but it keeps the process predictable through real delays and failures in connected services.
Make the integration understandable to the next team
Provide interface documentation, request examples, access procedures and a dependency list. Discuss external API limits, version changes and who receives error alerts. When a service lacks the required interface, review its supported options before proposing a fragile workaround the owner does not understand. Fees depend on documentation quality, both systems’ readiness and reliability requirements. External subscriptions and usage limits belong explicitly in the operating plan, not in hidden assumptions.
Two useful questions
Is connecting always easy when an API exists?
No. The required methods, permissions, limits, documentation and business rules all matter. Verify the actual journey before finalising the estimate.
Can an existing integration be preserved?
Yes. First document its contract and test journeys. Add new functionality without altering existing data or behaviour unless that change is specifically needed.