Introduction
SOSfinder gives you Secretary of State business-entity data for all 50 states through a single REST endpoint — entity status, registered agent, formation date, and more.
Every lookup goes through one unified endpoint. Pass a business name and a state, and SOSfinder returns the best match plus similar filings in one consistent schema for every state. Building with AI agents instead of raw HTTP? The hosted MCP server exposes these lookups as native tools for Claude, Cursor, and any other MCP client.
Quickstart
Authenticate with your secret key from the server side and GET /search with a state and a business name.
curl 'https://api.sosfinder.com/search?state=WY&business_name=Acme%20LLC' \
-H "x-api-key: $SOS_API_KEY"Next steps
Get a key and call the API securely.
How lookups are counted and billed.
The full request and response reference.
Limits, headers, and best practices.
Give Claude, Cursor, and other AI agents SOSfinder tools.
Every status the API returns and how to handle it.
Stuck on something the docs don’t cover? Email support@sosfinder.com and we’ll help you out.