For any commercial partner integration, the REST API is the backbone. It defines how your product talks to theirs — credentials, endpoints, request formats, response codes. When you work with a commercial partner, every field matters. Every method must be consistent, predictable, and fast.
A high-performing REST API for a commercial partner project starts with clean resource modeling. Use standard HTTP verbs for logical actions. Keep URL paths semantic and stable. Do not break existing endpoints without versioning. Commercial partner agreements often extend over years; your API has to remain dependable within those timelines.
Authentication is non-negotiable. For most commercial partner APIs, OAuth 2.0 or token-based authentication is the standard. Keep tokens short-lived and refreshable. Enforce TLS. Log every interaction between your systems and the partner's systems, but safeguard personally identifiable data.
Error handling builds trust. Use proper status codes — 200 for success, 400 for client errors, 500 for server errors. Include clear JSON error messages with enough detail for engineers to understand the cause and fix it. Partner developers should never need to guess what went wrong.