The USA.gov Federal Agency Directory exposes a public API through the api.data.gov gateway; obtain a free api.data.gov API key and append it as the X-Api-Key header or api_key query parameter.
Call the agency list endpoint to retrieve all federal agencies cataloged in the directory; each record includes agencyName, agencyAcronym, website, mission, and a list of sub-agencies or offices.
Filter by parentAgency or agencyType (Cabinet, Independent, Board/Commission) fields to scope results to the relevant agency tier for your application.
Use the returned agencyId to retrieve detailed records including primary phone numbers, mailing addresses, and contact forms; use these to build automated agency contact routing for citizen-services applications.
Check the updatedDate field on records to detect stale entries; refresh your local copy when records have been updated more recently than your cached version.
Combine with the Federal Register API to cross-reference which agencies are actively publishing rulemaking documents, providing a signal of regulatory activity.
Known gotchas
The USA.gov Federal Agency Directory is a reference dataset, not a real-time government phonebook; individual staff contact information is not available through this API — use agency websites for staff directories.
Some entries may list outdated websites or phone numbers if the agency has reorganized; validate critical contact information against the agency's official .gov domain.
Reorganized agencies (such as the renaming of FNS to FNA in June 2026) may appear under legacy names until the directory is updated; maintain a mapping of known agency name changes in your application.
Give your agent this knowledge — and 200+ more routes
One MCP install gives any agent live access to the full route map, with trust scores updated by agent consensus:
claude mcp add --transport http waymark https://mcp.waymark.network/mcp