generated: '2026-07-25'
method: searched
source: >-
  https://www.fca.org.uk/firms/financial-services-register ;
  https://www.fca.org.uk/publication/systems-information/fca-firds-tech-spec.pdf ;
  https://www.fca.org.uk/publication/systems-information/fca-fitrs-tech-spec.pdf ;
  live anonymous probes
note: >-
  The FCA runs two unrelated API surfaces with different conventions. Neither is
  described by an OpenAPI document, so everything below is either taken from an
  FCA published page/technical specification or observed in a live anonymous
  request, with the source named per item.
surfaces:
- api: FCA Financial Services Register API
  base_url: https://register.fca.org.uk/services/V0.1
  style: REST, read-only, JSON
  authentication:
    style: api key in two request headers (X-Auth-Email, X-Auth-Key)
    artifact: authentication/fca-uk-authentication.yml
  versioning:
    scheme: uri-path
    current: V0.1
    note: >-
      The version segment has been V0.1 since the API was introduced; the FCA
      publishes no version policy, no version-negotiation header and no
      deprecation schedule.
  resource_model:
    addressing: >-
      Resources are addressed by regulatory identifier — Firm Reference Number
      (FRN) for firms, Individual Reference Number (IRN) for individuals,
      Product Reference Number (PRN) for collective investment schemes.
    lookup_shape: one entity per request; there is no bulk or list-all operation
    bulk_alternative:
      name: Register Extract Service (RES)
      url: https://www.fca.org.uk/firms/financial-services-register/data-extract
      note: paid file delivery, the FCA's stated answer to the single-entity design limit
  pagination:
    supported: unknown
    note: >-
      No pagination contract is documented on any anonymously reachable FCA page.
      Community clients surface a ResultInfo block on search responses, but the
      FCA's own reference is behind the portal login, so nothing is asserted here.
  content_negotiation:
    request_header: 'Accept: application/json'
    response: application/json
  idempotency:
    supported: false
    reason: >-
      Read-only API. Every documented operation is a GET; there is no write
      surface and therefore no idempotency key contract. No Idempotency pointer
      is wired in apis.yml — its absence here is correct, not a gap.
  rate_limiting:
    documented: true
    limit: 50 requests per 10 seconds
    signalling: no documented rate-limit response headers
    artifact: rate-limits/fca-uk-rate-limits.yml
    confidence: medium
    source_note: >-
      The figure is stated in community client documentation and in the portal
      material; the FCA's own statement of it sits behind the developer portal
      login and could not be verified anonymously.
  error_envelope:
    shape: '{"Success":"false", "<message>"}'
    media_type: application/json
    rfc9457: false
    observed:
      request: GET https://register.fca.org.uk/services/V0.1/Firm/122702
      status: 403
      body: '{"Success":"false", "Sorry, this page is not available. Missing Headers."}'
    artifact: errors/fca-uk-problem-types.yml
  request_tracing:
    request_id_header: none observed
- api: FCA Data Publication API (FIRDS / FITRS)
  base_url: https://api.data.fca.org.uk
  style: OpenSearch/Elasticsearch query-string search over published file artefacts
  authentication:
    style: none (anonymous)
  versioning:
    scheme: none
    note: The index name is the resource; no version segment exists.
  resource_model:
    indices:
    - fca_data_firds_files
    - fca_data_fitrs_files
    note: >-
      Only these two indices, the two the FCA documents, respond anonymously.
      Every other index name probed returns 403 "Missing Authentication Token".
  query_parameters:
  - name: q
    required: true
    description: >-
      Elasticsearch query_string query. FIRDS searchable fields are file_type,
      file_name, publication_date; FITRS adds instrument_type. Wildcards and
      range syntax (publication_date:[YYYY-MM-DD TO YYYY-MM-DD]) are supported.
    source: FCA FIRDS/FITRS technical specifications, section 3.7
  - name: from
    required: true
    default: 0
    description: starting index of the hits to return
  - name: size
    required: true
    default: 10
    description: number of hits to return
  - name: sort
    required: false
    description: fieldName or fieldName:asc / fieldName:desc; multiple sort params allowed, order significant
  - name: pretty
    required: false
    description: pretty-print the JSON response
  - name: df
    required: false
    description: default field when the query term carries no field prefix
  - name: default_operator
    required: false
    default: OR
    description: AND or OR
  pagination:
    style: offset
    params: [from, size]
    response_field: hits.total
    note: >-
      The FCA technical specification describes cycling by advancing `from` in
      `size`-sized pages; hits.total gives the number of records found.
  response_envelope:
    shape: standard Elasticsearch search response
    fields: [took, timed_out, _shards, hits.total, hits.max_score, 'hits.hits[]._source']
    record_fields: [download_link, file_type, file_name, publication_date, last_refreshed]
    fitrs_extra_field: instrument_type
    media_type: application/json
    note: JSON is the only format available; the technical specification states this explicitly.
  idempotency:
    supported: false
    reason: read-only GET search interface; no write surface
  rate_limiting:
    documented: true
    limit: unquantified
    quote: >-
      "To minimise disruption to the FCA FIRDS service caused by irregular traffic
      patterns, malicious (e.g. DDOS) or accidental, all requests to both the UI
      Web Form and the API service will be rate limited." — FCA FIRDS technical
      specification, section 1.1 Acceptable Use. Individual file download links
      are explicitly excluded from throttling.
  error_envelope:
    shape: '{"message":"Missing Authentication Token"}'
    status_observed: 403
    rfc9457: false
cross_links:
  authentication: authentication/fca-uk-authentication.yml
  errors: errors/fca-uk-problem-types.yml
  lifecycle: lifecycle/fca-uk-lifecycle.yml
  rate_limits: rate-limits/fca-uk-rate-limits.yml
  data_model: data-model/fca-uk-data-model.yml