How it works
SP-API replaced Amazon's older MWS API. Apps register as developers, request roles that govern which data they may access, and authorize each seller through an OAuth-style flow. Data comes from operation endpoints and from asynchronous reports, which are often the sole source of settlement and fee detail. Rate limits are set per operation, and restricted data such as buyer addresses needs extra approval.
Example
A repricing tool uses SP-API to read a seller's listings and competitive prices, then submits price updates through the listings endpoints, within Amazon's rate limits for that operation.
In integrations
The Unify Orders API is designed to handle SP-API's authorization and roles and map orders, settlements and FBA inventory into the Unify Graph. Marketplace orders are read-only by design. Current status is on the Amazon integration page. SP-API is detailed but complex: roles, report types, restricted data and per-operation limits all need handling. Plan for asynchronous reports wherever you need financial detail.