ACS B01001: inspecting a release-specific variable group

The Census API group page for 2020 ACS 5-year B01001 identifies the group as Sex by Age and lists its variables with labels and types. The release path is part of the reference: 2020, acs, and acs5 should remain attached to any extracted variable list. That page distinguishes estimate variables, margin-of-error variables and annotation fields. For example, B01001_001E and B01001_001M occupy different roles even though their identifiers share a table and line number. An annotation field should not be interpreted as another population estimate. A reliable local catalog can store the dataset path, group identifier, variable name, full label, concept and declared type. Preserve the complete variable name instead of joining on a shortened prefix. Before combining two catalogs, compare the labels and roles for the precise variables involved. A syntactically similar name is a useful candidate match, not evidence of equivalence. Keep unmatched variables visible for editorial review. This note documents how to inspect metadata for one historical release. It contains no downloaded estimates, and it makes no claim that a current API response for another year has the same variable definitions.