Sign up at api.developer.attomdata.com to obtain your API key; a 30-day free trial sandbox is available for initial testing
Use the /propertyapi/v1.0.0/property/detail endpoint with an address or ATTOM ID parameter to retrieve detailed property characteristics for a specific parcel
For assessor data including tax assessment values and land/improvement breakdown, query /propertyapi/v1.0.0/assessment/detail
To pull sales history and comparable transactions, use /propertyapi/v1.0.0/sale/snapshot with address or geographic bounding-box parameters
For AVM-driven valuation, call /propertyapi/v1.0.0/attomavm/detail; the response includes the estimated value, confidence score, and value range
Paginate bulk requests using the page and pagesize query parameters; use the /property/address endpoint for address-matched lookups rather than raw parcel IDs when APN is unavailable
Known gotchas
ATTOM pricing starts around $95/month for basic access but scales rapidly for high-volume or multi-endpoint use; audit your expected request volume against their pricing tiers before committing
ATTOM data is aggregated from county assessor and recorder offices and is updated monthly — it is not a real-time source; for listing data you still need an MLS feed
Coverage and data freshness vary by county; rural or low-transaction-volume counties may have older assessor data than metro areas
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