Obtain a RentCast API key from the RentCast developer dashboard.
Call the rent estimate endpoint with the property address (or latitude/longitude), property type (e.g., single-family, apartment), number of bedrooms, and number of bathrooms as query parameters.
Parse the response to extract the rentEstimate (median), rentEstimateLow, and rentEstimateHigh fields along with the comparablesCount to gauge confidence.
Optionally request the comparables array to see the rental comps used in the estimate, including their addresses, rent amounts, and distance from the subject.
If the property is in a market with low comparables count (under 5), flag the estimate as low-confidence and surface this to end users.
Cache estimates per address with a TTL of 7–30 days depending on market volatility.
Known gotchas
RentCast estimates are based on active rental listings, not actual lease transactions, so they reflect asking rent rather than effective rent.
In rural or low-density markets, the API may return an estimate based on comps several miles away; the distance field in each comparable should be checked.
The API charges per call; do not call it on every page load — cache aggressively and only refresh when the user explicitly requests updated data.
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