Start creative session - Apostra

POST /api/v2/buyer/campaigns/{campaignId}/creative-sessions Starts a reviewable creative session and returns draft variants for the campaign. Use the session to compare directions, refine one, evaluate it, and finalize the approved output as a campaign Creative.

Request

Field	Type	Required	Notes
`storefrontId`	number	No	Connected creative-provider storefront when the engine requires one. Omit it for a buyer-provided model key.
`providerType`	string	Yes	Creative provider to use.
`request`	object	Yes	Provider-neutral creative request, including the brief and target format when needed.
`prompt`	string	No	Buyer-facing creative direction.
`language`	string	No	Supported BCP-47 language for generated audio: English, Dutch, Spanish, or Portuguese, such as `es` or `pt-BR`. Omit it to preserve the existing language selection.

For an AudioStack session, set language when the buyer specifies the spoken language. It generates the script and AudioStack speech in that language; it is not a translation request for other creative modalities.

{
  "storefrontId": 1725,
  "providerType": "audiostack",
  "language": "pt-BR",
  "prompt": "Create a 30-second audio ad for the new collection.",
  "request": {
    "format_kind": "audio_hosted",
    "params": { "duration_ms_exact": 30000 },
    "creative_brief": {
      "prompt": "A warm introduction to the new collection."
    }
  }
}

Returns 201 Created with the creative session, including its draft variants and creative plan.