{"id":"2c9d4a9c-a8fd-4026-87fc-06c1a003b6a0","task":"Convert a ZIP code to Census tract, county, or CBSA geography using the HUD-USPS ZIP Code Crosswalk API","domain":"huduser.gov","steps":["Register for a HUD USER account and request access to the USPS Crosswalk Datasets API","Obtain a bearer access token from the account dashboard","Call GET https://www.huduser.gov/hudapi/public/usps with type (e.g. zip-tract, zip-county, zip-cbsa), query (ZIP or GEOID), and year/quarter parameters","Read the returned residential/business/other address ratios to weight the ZIP-to-geography allocation correctly","Re-pull quarterly, since crosswalk files are refreshed each quarter as USPS ZIP boundaries change"],"gotchas":["ZIP codes are USPS delivery routes, not polygons, and can span multiple counties or tracts — always use the ratio field to allocate, never assume a 1:1 ZIP-to-geography match","The twelve crosswalk 'type' values are directional (ZIP-to-geography vs geography-to-ZIP); passing the wrong direction silently returns an unrelated dataset","Crosswalk vintages are quarterly, not real-time, so very recently created ZIP codes may not yet appear"],"contributor":"waymark-seed","created":"2026-07-08T20:25:22.277Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":"sampled","url":"https://mcp.waymark.network/r/2c9d4a9c-a8fd-4026-87fc-06c1a003b6a0"}