> ## Documentation Index > Fetch the complete documentation index at: https://vaquill.ai/docs/llms.txt > Use this file to discover all available pages before exploring further. # Old-vs-new text for one change > The section's text before and after this specific change, when available (see `hasDiff` on the change list above). Only meaningful for `amended` (both sides) and `removed` (before only); `added` has nothing to diff against, so `hasBefore`/`hasAfter` are always false there. A missing side is not an error: `hasBefore`/`hasAfter` say which text is actually present, so a caller can render a graceful 'diff unavailable' state for older changes or a snapshot that failed to capture, instead of treating null as a failure. **Cost**: 4 credits per call (see `/api-credits/pricing`). This is the only metered route in the alerts family: every other board and watch endpoint, including the `/changes` list this reads from, is free. A diff that resolves NEITHER side is refunded in full and reports `creditsConsumed: 0` -- an empty envelope is not an answer. A one-sided diff IS the complete answer for a `removed` or `added` change and is charged normally. ## OpenAPI ````yaml https://api.vaquill.ai/external/openapi.json get /api/v1/watches/{watch_id}/changes/{change_id}/diff openapi: 3.1.0 info: title: Vaquill Developer API description: >- Public API for legal statutes and legislation. **Authentication**: Pass your API key via the `Authorization: Bearer vq_key_...` header. **Credits**: Each call costs API credits. See `GET /api/v1/api-credits/pricing` for the full pricing matrix. ## Jurisdictions | Jurisdiction | Coverage | `countryCode` | |---|---|---| | **United States** | USC, CFR, nearly all 50 state statutory codes (plus DC and Puerto Rico), state constitutions, and court rules. | `US` | See the full [Coverage page](https://www.vaquill.ai/docs/coverage) for the jurisdiction-by-jurisdiction breakdown, or call `/us/statutes/coverage` for live counts. ## Endpoints - **US Statutes**: Search and retrieve USC, CFR, state statutes, constitutions, court rules, executive orders, and regulations with full text - **Board Watches**: Subscribe to a corpus source and get a webhook or email when it refreshes with real changes (free, API key required) - **Pricing**: Credit costs per endpoint (no auth required) ## Rate limits Limits are enforced per API key and scale with your plan. A `429` response includes a `Retry-After` header. | Plan | Per minute | Per hour | Per day | |---|---|---|---| | Vaquill API Pro | 30 | 500 | 1,000 | | Vaquill API Business | 150 | 2,500 | 10,000 | For full documentation, visit the [API Reference](https://www.vaquill.ai/docs/api-reference/). version: 1.0.0 contact: name: Vaquill API Support url: https://www.vaquill.ai email: support@vaquill.ai license: name: Proprietary url: https://www.vaquill.ai/terms termsOfService: https://www.vaquill.ai/terms servers: - url: https://api.vaquill.ai description: Production security: - ApiKeyAuth: [] tags: - name: US Statutes description: >- Search and retrieve US statutes. Covers the United States Code (USC), Code of Federal Regulations (CFR), all 50 state statutes, constitutions, court rules, executive orders, Federal Register agency rules, agency guidance, and state regulations. Scope a search with the `corpusType` filter. - **Search**: Search across all USC, CFR, state, and regulatory sections - **Section**: Get metadata, citation, hierarchy, and source links for a specific section - **Body**: Get the full text of a section - name: Board Watches description: >- Law-change alerts. Subscribe to a **board** (a tracked corpus source, identified by `corpusType` plus an optional `state`) and get a webhook or email whenever it refreshes with real changes, naming the exact sections that changed. Fetch old-vs-new text for any amended section via the change diff. Boards refresh on their own existing cadence; watching one does not change how often it refreshes. Every endpoint here is **free**: authenticated by API key and rate-limited, but not credit-metered. See the [Law Change Alerts guide](https://www.vaquill.ai/docs/api-guide/alerts) for the full walkthrough. - name: Pricing description: >- Credit pricing and conversion rates. No authentication required. 1 credit = $0.01 USD. externalDocs: description: Full API Reference url: https://www.vaquill.ai/docs/api-reference/ paths: /api/v1/watches/{watch_id}/changes/{change_id}/diff: get: tags: - Board Watches summary: Old-vs-new text for one change description: >- The section's text before and after this specific change, when available (see `hasDiff` on the change list above). Only meaningful for `amended` (both sides) and `removed` (before only); `added` has nothing to diff against, so `hasBefore`/`hasAfter` are always false there. A missing side is not an error: `hasBefore`/`hasAfter` say which text is actually present, so a caller can render a graceful 'diff unavailable' state for older changes or a snapshot that failed to capture, instead of treating null as a failure. **Cost**: 4 credits per call (see `/api-credits/pricing`). This is the only metered route in the alerts family: every other board and watch endpoint, including the `/changes` list this reads from, is free. A diff that resolves NEITHER side is refunded in full and reports `creditsConsumed: 0` -- an empty envelope is not an answer. A one-sided diff IS the complete answer for a `removed` or `added` change and is charged normally. operationId: >- get_watch_change_diff_api_v1_watches__watch_id__changes__change_id__diff_get parameters: - name: watch_id in: path required: true schema: type: string title: Watch Id - name: change_id in: path required: true schema: type: integer title: Change Id responses: '200': description: The change's before/after text (either side may be absent). content: application/json: schema: {} example: data: changeId: 91 changeKind: amended beforeText: An application for approval of a new drug... afterText: >- An application for approval of a new drug or amended new drug... hasBefore: true hasAfter: true meta: processingTimeMs: 41 creditsConsumed: 4 '401': description: Invalid or missing API key. content: application/json: schema: $ref: '#/components/schemas/ApiDetailError' '402': description: Insufficient API credits. content: application/json: schema: $ref: '#/components/schemas/ApiDetailError' '403': description: API key lacks `research:read` scope. content: application/json: schema: $ref: '#/components/schemas/ApiDetailError' '404': description: Watch not found, or the change is not covered by this watch. content: application/json: schema: $ref: '#/components/schemas/ApiDetailError' '422': description: Validation Error content: application/json: schema: $ref: '#/components/schemas/HTTPValidationError' '429': description: Rate limit exceeded. content: application/json: schema: $ref: '#/components/schemas/ApiDetailError' components: schemas: ApiDetailError: properties: detail: type: string title: Detail description: >- Human-readable reason, safe to surface to an end user. Branch on the HTTP status rather than on this string: the wording is not part of the contract and may be reworded, but 401 (bad key), 402 (out of credits), 403 (missing scope), 404 (no such resource) and 429 (rate limited) are stable. examples: - Insufficient API credits. type: object required: - detail title: ApiDetailError description: |- Error envelope the API actually returns. All errors (401/402/403/404/422/429/5xx) come back as a single `detail` string (FastAPI default), e.g. `{"detail": "Insufficient API credits."}`. Documenting the real shape so client code can rely on it. HTTPValidationError: properties: detail: items: $ref: '#/components/schemas/ValidationError' type: array title: Detail type: object title: HTTPValidationError ValidationError: properties: loc: items: anyOf: - type: string - type: integer type: array title: Location msg: type: string title: Message type: type: string title: Error Type type: object required: - loc - msg - type title: ValidationError securitySchemes: ApiKeyAuth: type: http scheme: bearer bearerFormat: vq_key_* description: >- API key issued from the developer dashboard. Pass as `Authorization: Bearer vq_key_...` ````