> ## Documentation Index > Fetch the complete documentation index at: https://docs.closient.com/llms.txt > Use this file to discover all available pages before exploring further. # Compose a GS1 Digital Link URI from Application Identifiers > Build a spec-ordered Digital Link URI from a primary key plus optional qualifiers and data attributes, and grade the result. Qualifiers and attributes are **repeated** query parameters in `code:value` form — `?qualifier=10:LOT1&qualifier=21:SN1&attribute=17:261231` — which keeps the whole request in the URL and therefore cacheable. A token missing its `:` is reported as an `error` issue rather than dropped, so a URI is never silently composed without data you asked for. **Keyless** — no API key, no signup. IP-throttled at 300 requests/minute and cached at the edge for 24h, so repeat calls for the same input do not reach origin. Over-rate callers get a `429` with a `Retry-After` header and a `retry_after` field — it never silently degrades or returns a wrong answer under load. ## OpenAPI ````yaml /openapi/openapi-resolver.json get /resolver/api/v1/public/gs1/build openapi: 3.1.0 info: title: Resolver API version: 1.0.0 description: > GS1 Digital Link resolution with content negotiation and linkset support. ## Authentication All endpoints require an API key passed via the `X-API-Key` HTTP header, unless otherwise noted. ``` X-API-Key: csb__ ``` Generate API keys in **Settings > API Keys** in your dashboard, or via the Account API. Session-based (cookie) authentication is also accepted for browser-based access. ## Rate Limits | Tier | Requests / minute | Requests / day | |-------------|-------------------|----------------| | Default | 300 | 10,000 | | Custom | Contact us | Contact us | Rate-limit headers are included on every response so callers can self-throttle without hitting our 429s ("informed governor"): - `RateLimit-Policy` — every active window, e.g. `300;w=60, 10000;w=86400` - `RateLimit-Limit` — quota for the **most-restrictive** currently-active window - `RateLimit-Remaining` — requests left in that window - `RateLimit-Reset` — seconds until that window resets (relative; clock-skew safe) Legacy `X-RateLimit-*` aliases are also emitted for back-compat. `X-RateLimit-Reset` keeps the absolute Unix-timestamp shape to avoid breaking existing consumers. When rate-limited, you receive `429 Too Many Requests` with a `retry_after_seconds` field in the error envelope and a `Retry-After` header. ## Pagination List endpoints return paginated results in this envelope: ```json { "data": [...], "pagination": { "page": 1, "page_size": 25, "total_count": 342, "total_pages": 14, "has_next": true, "has_previous": false } } ``` Use `?page=2&page_size=50` query parameters. Maximum page size is 100. ## Error Responses All errors conform to [RFC 9457 Problem Details](https://www.rfc-editor.org/rfc/rfc9457) with `Content-Type: application/problem+json`: ```json { "type": "https://closient.com/docs/errors/not_found", "title": "Not Found", "status": 404, "detail": "The requested resource was not found.", "error_code": "not_found", "retryable": false, "timestamp": "2026-03-31T12:00:00+00:00" } ``` Common error codes: `unauthorized` (401), `forbidden` (403), `not_found` (404), `validation_error` (422), `rate_limited` (429), `internal_error` (500). termsOfService: https://www.closient.com/terms/ servers: - url: https://www.closient.com security: [] tags: - name: Resolver description: GS1 Digital Link resolution with content negotiation and linkset support. - name: Custom URLs description: >- Reusable custom-URL catalog (C-3339) — create, list, edit, and delete the custom redirect destinations that resolution rules point at. - name: Verification description: >- Serial verification (`gs1:verificationService`) — tiered, rate-limited responses for serialized GTIN scans. Experimental v1; see the verification-service guide. - name: GS1 Primitives (Public) description: >- Keyless GS1 Digital Link primitives (C-4295) — parse, validate, build, decompress, and check-digit analysis. **No API key, no signup.** Pure functions over strings: no database, no network, no catalog data. IP-throttled and edge-cached so repeat calls cost nothing. This is the reference implementation the resolver itself runs on. - name: Resolver Custom Hostnames description: >- BYO domain (C-4058) — register a customer-owned hostname, publish the CNAME records, verify ownership, and serve an org's Digital Link QRs from its own DNS. externalDocs: description: Closient Documentation url: https://docs.closient.com paths: /resolver/api/v1/public/gs1/build: get: tags: - GS1 Primitives (Public) summary: Compose a GS1 Digital Link URI from Application Identifiers description: >- Build a spec-ordered Digital Link URI from a primary key plus optional qualifiers and data attributes, and grade the result. Qualifiers and attributes are **repeated** query parameters in `code:value` form — `?qualifier=10:LOT1&qualifier=21:SN1&attribute=17:261231` — which keeps the whole request in the URL and therefore cacheable. A token missing its `:` is reported as an `error` issue rather than dropped, so a URI is never silently composed without data you asked for. **Keyless** — no API key, no signup. IP-throttled at 300 requests/minute and cached at the edge for 24h, so repeat calls for the same input do not reach origin. Over-rate callers get a `429` with a `Retry-After` header and a `retry_after` field — it never silently degrades or returns a wrong answer under load. operationId: apps_resolver_api_public_gs1_build_digital_link_public parameters: - in: query name: primary_ai schema: description: The primary identifier AI code, e.g. `01` for GTIN. maxLength: 4 minLength: 2 title: Primary Ai type: string required: true description: The primary identifier AI code, e.g. `01` for GTIN. - in: query name: primary_value schema: description: The primary identifier's value, e.g. `09506000164908`. maxLength: 256 minLength: 1 title: Primary Value type: string required: true description: The primary identifier's value, e.g. `09506000164908`. - in: query name: qualifier schema: default: [] description: Repeatable qualifier AI in `code:value` form, e.g. `10:LOT1`. items: type: string title: Qualifier type: array required: false description: Repeatable qualifier AI in `code:value` form, e.g. `10:LOT1`. - in: query name: attribute schema: default: [] description: >- Repeatable data-attribute AI in `code:value` form, e.g. `17:261231`. items: type: string title: Attribute type: array required: false description: Repeatable data-attribute AI in `code:value` form, e.g. `17:261231`. - in: query name: scheme schema: default: https description: >- URI scheme; `http` or `https`. Anything else is reported as an issue and the default is used. maxLength: 16 title: Scheme type: string required: false description: >- URI scheme; `http` or `https`. Anything else is reported as an issue and the default is used. - in: query name: host schema: default: id.example.com description: Resolver host to compose against, e.g. `id.gs1.org`. maxLength: 255 title: Host type: string required: false description: Resolver host to compose against, e.g. `id.gs1.org`. responses: '200': description: OK content: application/json: schema: $ref: '#/components/schemas/DigitalLinkBuildOut' components: schemas: DigitalLinkBuildOut: description: A composed Digital Link URI plus how it graded. examples: - data_attributes: - code: '17' description: Expiration date kind: attribute name: Expiration date value: '261231' host: id.gs1.org is_conformant: true issues: [] permitted_qualifier_codes: - '10' - '21' - '22' primary: code: '01' description: Global Trade Item Number kind: primary name: GTIN value: '09506000164908' qualifiers: - code: '10' description: Batch or lot number kind: qualifier name: Batch/Lot value: LOT1 scheme: https uri: https://id.gs1.org/01/09506000164908/10/LOT1?17=261231 properties: uri: anyOf: - type: string - type: 'null' description: >- The composed URI, or `null` when the inputs were too incomplete to compose one. title: Uri is_conformant: description: True when the composed URI carries no `error`-severity issues. title: Is Conformant type: boolean issues: description: Every issue found while composing. items: $ref: '#/components/schemas/DigitalLinkIssueOut' title: Issues type: array scheme: description: >- The scheme actually used (normalised; defaults apply when input was blank). title: Scheme type: string host: description: >- The host actually used (normalised; defaults apply when input was blank). title: Host type: string primary: anyOf: - $ref: '#/components/schemas/ParsedAIOut' - type: 'null' description: The primary identifier AI, or `null` when none was supplied. qualifiers: description: Qualifier AIs written into the path. items: $ref: '#/components/schemas/ParsedAIOut' title: Qualifiers type: array data_attributes: description: Data attributes written into the query string. items: $ref: '#/components/schemas/ParsedAIOut' title: Data Attributes type: array permitted_qualifier_codes: description: >- Which qualifier AI codes this primary key permits — use it to drive a picker. examples: - - '10' - '21' - '22' items: type: string title: Permitted Qualifier Codes type: array required: - is_conformant - scheme - host title: DigitalLinkBuildOut type: object DigitalLinkIssueOut: description: One pass/fail row from a validation or build report. examples: - code: invalid_check_digit message: 'GTIN check digit is invalid: expected 8, got 7.' severity: error properties: code: description: >- Stable machine-readable issue code, safe to branch on (e.g. `unknown_primary_ai`). title: Code type: string severity: $ref: '#/components/schemas/DigitalLinkIssueSeverityEnum' description: >- `error` blocks conformance; `warning` is advisory and leaves `is_conformant` intact. message: description: Human-readable explanation of the issue. title: Message type: string required: - code - severity - message title: DigitalLinkIssueOut type: object ParsedAIOut: description: One Application Identifier extracted from (or composed into) a URI. examples: - code: '01' description: >- Global Trade Item Number — the primary key identifying the trade item. kind: primary name: GTIN value: '09506000164908' properties: code: description: The GS1 Application Identifier code. examples: - '01' title: Code type: string name: description: Human-readable AI name. examples: - GTIN title: Name type: string kind: $ref: '#/components/schemas/DigitalLinkAIKindEnum' description: >- Whether the AI identifies the item (`primary`), narrows it (`qualifier`), or describes it (`attribute`). value: description: The AI's value as it appears in the URI. examples: - '09506000164908' title: Value type: string description: description: What this AI means in the GS1 General Specifications. title: Description type: string required: - code - name - kind - value - description title: ParsedAIOut type: object DigitalLinkIssueSeverityEnum: description: |- Whether a Digital Link report row blocks conformance or only advises. Mirrors the ``Literal["error", "warning"]`` on :class:`apps.resolver.gs1_digital_link_validator.ValidationIssue`. An ``ERROR`` is what drives ``is_conformant`` to ``false``; a ``WARNING`` is spec-legal but discouraged (an uppercase host, say) and leaves conformance intact. enum: - error - warning title: DigitalLinkIssueSeverityEnum type: string DigitalLinkAIKindEnum: description: |- Where an Application Identifier sits in a Digital Link URI. ``PRIMARY`` is the identifying key (AI 01 GTIN, 414 GLN, 00 SSCC, ...) and there is exactly one. ``QUALIFIER`` narrows that key within the URI path (AI 10 lot, 21 serial, 22 CPV). ``ATTRIBUTE`` rides on the query string and carries data *about* the item (AI 17 expiry, 3103 net weight) rather than identifying it. enum: - primary - qualifier - attribute title: DigitalLinkAIKindEnum type: string ````