> ## Documentation Index > Fetch the complete documentation index at: https://docs.fourdos.dev/llms.txt > Use this file to discover all available pages before exploring further. # Fill one ad slot > Called from the club's page with its publishable `ek_live_` key; the request `Origin` must be on the key's allowlist and must be the ad unit's property. Without `identity_token` the viewer is anonymous. With a valid one the slot is targeted at that member, and when the fan holds the club's personalised content consent the impression and click are recorded against the member; otherwise they are recorded anonymously. A missing, malformed, expired or other-club token, and the unsigned `member_external_id` and `user_id` parameters older integrations send, all serve the request anonymously rather than failing. No sponsor surface ever shows a member. ## OpenAPI ````yaml https://api.develop.fourdos.dev/openapi/partner.json get /v1/ads/serve openapi: 3.1.0 info: title: 4D OS Partner API version: 0.1.0 description: >- REST API for 4D OS partners. Authenticate with your organization API key: `Authorization: Bearer `. Requests and responses are JSON with `snake_case` field names. Errors share one envelope: `{ "error": { "code", "status", "message", "details"? } }`. Mutating endpoints that declare it accept an `Idempotency-Key` header so retries are safe. Bulk-migrating members? See the [Migrating to 4D guide](https://docs.fourdos.dev/walkthroughs/migrate-existing-members) for the canonical import schema, a worked example, and the `/v1/imports` sequence. servers: - url: https://api.develop.fourdos.dev security: - partnerApiKey: [] tags: - name: Users description: Create, read, and manage users and their org membership - name: Imports description: Bulk member import jobs (staging → validate → commit) - name: API keys description: Issue, list, and revoke server-side organization API keys - name: Modules description: >- Publish private modules, install visible modules, and manage their credentials - name: Ingest description: Receive signed native events from an installed module - name: Engagement description: Browser event tracking (publishable keys) and tracking-key management - name: Revenue description: Report sales and refunds for the club's revenue dashboards - name: Ad delivery description: Fill a club site's ad slots, for anonymous or signed-in fans - name: Ad entries description: Fans entering a sponsor's draw, reported by the club's backend paths: /v1/ads/serve: get: tags: - Ad delivery summary: Fill one ad slot description: >- Called from the club's page with its publishable `ek_live_` key; the request `Origin` must be on the key's allowlist and must be the ad unit's property. Without `identity_token` the viewer is anonymous. With a valid one the slot is targeted at that member, and when the fan holds the club's personalised content consent the impression and click are recorded against the member; otherwise they are recorded anonymously. A missing, malformed, expired or other-club token, and the unsigned `member_external_id` and `user_id` parameters older integrations send, all serve the request anonymously rather than failing. No sponsor surface ever shows a member. operationId: serveAd parameters: - name: key in: query required: true schema: type: string description: Publishable `ek_live_` tracking key. - name: unit in: query required: true schema: type: string description: Ad unit code. - name: identity_token in: query required: false schema: type: string description: From `POST /v1/ads/identity-tokens`, for a signed-in fan. responses: '200': description: 'A fill, or `{ ad: null, reason: "no_fill" }`' content: application/json: schema: $ref: '#/components/schemas/ServedAd' '401': description: Missing, unknown or revoked key content: application/json: schema: $ref: '#/components/schemas/Error' '403': description: Origin missing or not on the key's allowlist content: application/json: schema: $ref: '#/components/schemas/Error' '429': description: Ad serve rate limit exceeded for this key content: application/json: schema: $ref: '#/components/schemas/Error' components: schemas: ServedAd: type: object properties: ad: type: - object - 'null' properties: creative_id: type: string format: uuid campaign_id: type: string format: uuid unit_code: type: string width: type: integer height: type: integer format: type: string asset_url: type: string format: uri click_url: type: string format: uri description: The platform's click redirector, never the advertiser's URL. impression_url: type: string format: uri token: type: string description: Signed serve token for the impression beacon and the click. required: - creative_id - campaign_id - unit_code - width - height - format - asset_url - click_url - impression_url - token reason: type: string enum: - no_fill description: Present when `ad` is null. required: - ad Error: type: object properties: error: type: object properties: code: type: string status: type: integer message: type: string details: type: object additionalProperties: true required: - code - status - message required: - error securitySchemes: partnerApiKey: type: http scheme: bearer description: >- Organization API key (`org_...`) sent as `Authorization: Bearer `. Keys are scoped to one organization; every request operates within that tenant. ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.