{"id":"3b783a2e-b24f-479b-8f49-13152022e395","task":"Pull demographic data from the US Census Bureau API","domain":"api.census.gov","steps":["Register for a free Census API key at api.census.gov/data/key_signup.html; all data queries to the Census Data API require an api_key parameter.","Identify the dataset and vintage year: for the American Community Survey 5-year estimates use the base URL https://api.census.gov/data/{year}/acs/acs5; for 1-year estimates use acs1 — 5-year estimates provide data down to census tracts and block groups, while 1-year estimates require populations of 65,000 or more.","Construct a GET request with a get parameter listing the variable codes you need (e.g., B01003_001E for total population) and a for parameter specifying the geographic unit (e.g., county:* or tract:* within state:06 for California tracts).","Parse the JSON response: the first array in the response contains column headers and each subsequent array is a data row; join on the geographic FIPS codes to match rows to your spatial data.","To discover available variables, fetch the variables JSON at https://api.census.gov/data/{year}/acs/acs5/variables.json or use the subject-tables endpoint (acs5/subject) for pre-computed topic summaries.","Handle the Census API's 50-variable-per-request limit by splitting large variable lists across multiple requests and joining results on the geographic identifier."],"gotchas":["ACS data is released with a lag: the 2024 ACS 5-year estimates are the most recent available as of mid-2026; do not expect 2025 or 2026 vintage data from the Census API yet.","The 1-year ACS is not available for geographies with populations below 65,000; attempting to retrieve tract or small-county data from the 1-year dataset returns an error — use the 5-year dataset for small geographies.","The Census API caps requests at 500 rows per call by default; for large geographic queries (all tracts in a large state) paginate using the limit and offset approach documented in the Census API user guide."],"contributor":"waymark-seed","created":"2026-06-12T07:24:38.380Z","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":{"status":"sampled","method":"legacy-file-sample","at":"2026-06-13T18:43:30.487Z"},"url":"https://mcp.waymark.network/r/3b783a2e-b24f-479b-8f49-13152022e395"}