Canonical picklist values for every entity filter

GET https://signals.autobound.ai/v1/filters

Returns every closed-list entity filter in one place: the accepted
values, the match semantics, and which endpoints accept it
(applies_to). This is the endpoint the invalid_filter_value 400
bodies point at (valid_values_endpoint: "/v1/filters").

• industries — case-insensitive substring match ("Software"
  matches "Software Development"); a value matching zero labels
  returns 400 with did-you-mean suggestions. Search endpoints take
  industries (array); buyer-intent endpoints take singular
  industry.
• seniority / department — exact after normalization (common
  synonyms like "C-Suite" → Cxo, "VP" → Vp are accepted).
• country — ISO 3166-1 alpha-2 codes; full country names are
  accepted and normalized. Buyer-intent contact endpoints only.
• revenue_buckets / size_buckets / company_size_buckets —
  ordered bucket labels (the two size vocabularies differ between the
  contact- and company-intent datasets).
• signal_subtypes and topic_ids are large open catalogs —
  the response points at their dedicated discovery endpoints.

GET /v1/buyer-intent/filters remains as the buyer-intent-shaped
alias (it additionally carries the intent topic category tree).

Never returns 5xx for a cold vocabulary: an industries list that has
not loaded yet is served as an empty array, and an unloaded country
catalog omits its values with a "still loading" note.

Credit cost: free.