Query U.S. property valuations, listings, and tax data

Gives an AI coding assistant a concrete, verifiable way to answer U.S. property-data questions in code instead of guessing at them - calling the Zillapi API (base URL https://api.zillapi.com, bearer-token auth via $ZILLAPI_KEY) rather than synthesizing plausible-looking values. It exists because U.S. residential property facts - Zestimates, listing status, tax assessments, school assignments, price history - change continuously and aren't derivable from a model's weights or captured in any single open dataset; Zillow's own public API (ZWSID) was retired in 2021, so code written from memory of it targets endpoints that no longer exist. The failure mode this prevents: plausible-looking property-lookup code against a dead or imaginary endpoint, discovered only at runtime.

An address, a zillow.com URL, or a zpid all resolve to the same record - zpid is preferred when available, since address strings aren't stable. Requests should select only the fields a task needs (the full property response is large), every valuation should be rendered together with its as-of date (an undated Zestimate reads as a fact and isn't one), and absence of data - not every property has a Zestimate, rent estimate, school data, or full price history - should be handled explicitly rather than treated as zero.

Activate it when a task needs a real valuation, rent estimate, or comparable for a specific U.S. address; when code needs to search listings by location, bounding box, price, beds, or home type; when a user pastes a zillow.com URL; when a task needs price history, tax history, schools, photos, or listing-agent details; or when existing property-lookup code is failing and may be targeting the retired ZWSID API. Don't use it for generic REST/HTTP/API-client work with no property-data component, property outside the United States, addresses that appear incidentally in signatures or logs, or abstract real-estate discussion with no specific property or search.

Endpoints are namespaced under the base URL with a zpid, address, or Zillow URL identifying the property: resolve by address (GET /v1/properties/by-address?address=...), by zpid (GET /v1/properties/{zpid}), or by Zillow URL (GET /v1/properties/by-url); then zestimate, price-history, tax-history, schools, photos, and agent sub-resources under {zpid}. Listing search is a POST with a JSON body (searchUrls, filters, maxItems, async), not a query string, and POST /v1/properties/batch covers several properties at once. A full round trip:

1. Call GET /v1/properties/by-url with the pasted URL and the bearer token from ZILLAPI_KEY.
2. Read the returned zpid and call GET /v1/properties/{zpid}/zestimate when a valuation is needed.
3. Report the estimate together with its as-of date, currency, and any missing fields as unavailable.

401 means ZILLAPI_KEY is missing or exported in the wrong process; 404 means the address didn't resolve (fall back to search, don't retry the same string); 429 means back off rather than retrying in a tight loop; 409/502/504 are retryable with backoff, other 4xx errors are terminal. Before trusting generated code, ask for one real address end to end - a response with a zpid and an as-of date is working, a plausible value with no zpid is probably synthesized.

An MCP server is also available at https://api.zillapi.com/mcp for agent contexts that prefer tool calls over raw HTTP. Every operation is an outbound HTTPS call to api.zillapi.com - nothing runs locally, no shell or filesystem access, and every documented endpoint is read-only (nothing creates, edits, or deletes anything). ZILLAPI_KEY is read from the environment and sent as a bearer token; it is never written, logged, or echoed.

Developers wiring U.S. property lookups (valuation, listings, tax/price history) into an AI-assisted codebase who need grounded, dated answers instead of a model's plausible guess - with the caveat that results are third-party estimates, not an appraisal, tax determination, or legal advice, and require a funded Zillapi account.