---
title: "Select an attested source observation as of a date"
method: GET
path: "/api/v1/as-of/{source_id}"
tags: ["Integrity"]
---

# Select an attested source observation as of a date

`GET /api/v1/as-of/{source_id}`

## Request

- Base URL: `https://fonteum.com`
- URL: `https://fonteum.com/api/v1/as-of/{source_id}`
- Auth: none required

Public dataset-grain point-in-time read using methodology as-of-snapshot/v2. Only source observations with a matching usable SHA-256 attestation are selectable. The returned half-open selection window identifies which stored observation answers the requested date; it does not prove that the upstream source changed or remained unchanged between observations. Evidence-storage failures return 500 instead of a partial record.

## Path parameters

- `source_id` 'oig_leie' | 'nppes' | 'pecos_ppef' | 'cms_pos_facilities' | 'cms_care_compare_nh' | 'cms_qpp_mips_individual' | 'cms_open_payments' | 'cms_care_compare_dialysis' | 'cms_care_compare_hospice' | 'cms_civil_money_penalties', required

## Query parameters

- `date` union
  - string, date
  - string, date-time

## Response `200`

Attested as-of result. Coverage states such as no_attested_captures are successful reads and remain HTTP 200.

- AsOfSnapshotResponse: Version 2 dataset-level as-of result. Public selection admits only source observations with a matching usable SHA-256 attestation. Selection windows identify which stored observation answers the requested date; they do not prove that upstream content changed or stayed unchanged between observations.
  - `status` 'found' | 'before_tracking' | 'no_captures' | 'no_attested_captures', required: found selects an attested observation; before_tracking predates public attested coverage; no_captures means no stored observations exist; no_attested_captures means stored observations exist but none satisfy the public attestation boundary.
  - `source` object, required
    - `source_id` string, required
    - `label` string, required
    - `authority` string, required
    - `official_url` string, uri, required
    - `record_noun` string, required
  - `as_of` string, date, required: Requested point in time normalized to a UTC date.
  - `record` object, nullable, required: Selected observation and its half-open selection window; null unless status is found.
    - `snapshot_id` integer, required
    - `snapshot_date` string, date, required
    - `record_count` integer, nullable, required
    - `source_release_date` string, date, nullable, required: Publisher release date when recorded; separate from the stored observation and selection dates.
    - `capture_methodology` string, nullable, required
    - `selection_from` string, date, required: Inclusive start of the selected observation's public coverage window.
    - `selection_to` string, date, nullable, required: Exclusive date of the next usable attested observation; null for the latest one.
    - `is_latest_attested_observation` boolean, required
  - `attestation` object, nullable, required: Stored re-check trail for the selected observation; null unless status is found. Null witness or chain fields mean a complete evidence read found no corresponding row, not that the read failed.
    - `snapshot_id` integer, required
    - `content_hash` string, required: SHA-256 value stored on the matching attestation row.
    - `hash_algorithm` 'SHA-256', required
    - `attested_at` string, date-time, required
    - `witnessed` boolean, required
    - `witness_signature` string, nullable, required
    - `public_key_fingerprint` string, nullable, required
    - `chain_link_index` integer, nullable, required
    - `chain_link_signature` string, nullable, required
    - `corrections` object[], required
      - `correction_id` string, required
      - `wrong_value` string, required
      - `corrected_value` string, required
      - `reason` string, required
      - `issued_at` string, date-time, required
    - `verify_url` string, uri, required
    - `verify_api_url` string, uri, required
    - `chain_recheck_url` string, uri, required
    - `key_url` string, uri, required
  - `coverage` object, required: Coverage over usable attested observations only; staged observations without matching attestations are excluded.
    - `first_captured` string, date, nullable, required
    - `last_captured` string, date, nullable, required
    - `capture_count` integer, required
  - `methodology_version` 'as-of-snapshot/v2', required

## Other responses

- `400`: date/at is not a valid ISO date or timestamp.
- `404`: source_id is not in the curated public as-of source allowlist.
- `500`: Capture, attestation, witness, or chain evidence could not be read completely; no partial result is returned.

---

[API](https://skmtc.dev/fonteum/apis/fonteum-api.md) · [All operations](https://skmtc.dev/fonteum/apis/fonteum-api/llms.txt) · [OpenAPI document](https://skmtc.dev/fonteum/apis/fonteum-api/revisions/334e6e179d0d?raw)