Skip to main content
accept_proposal is the single terminal action for the compact proposal lifecycle. It accepts exactly one committed immutable proposal snapshot. committed retains the AdCP 3.1 reservation guarantee: the seller has locked the proposal’s commercial terms and reserved its inventory until expires_at. Finalization creates that hold; acceptance consumes it and creates, amends, or cancels the MediaBuy. Depending on proposal_kind, acceptance:
  • creates a new MediaBuy;
  • applies an amendment to an existing MediaBuy; or
  • applies a negotiated cancellation.
The proposal already carries the commercial terms, so the request does not repeat packages, dates, targeting, or creatives. Request schema: /schemas/3.0.23/media-buy/accept-proposal-request.json
For scalable proposals, include total_budget. If the proposal carries a signature-required insertion order, include io_acceptance. If the proposal belongs to an opportunity, acceptance closes that planning cycle with accepted_with_seller; callers may repeat the matching opportunity ID explicitly, while the accepted proposal retains the association. Success returns the resulting MediaBuy identity, the proposal with proposal_status: "accepted", and purchase_bindings[] mapping proposal purchase positions to package IDs for later creative assignment. Acceptance is idempotent. The seller atomically verifies proposal_id, proposal_terms_digest, expiry, and any base_media_buy_revision; stale or mismatched acceptance never applies different terms. A completed acceptance MAY include warnings[] for non-blocking observations at the commitment boundary. Each warning identifies its package through the returned media_buy_id and purchase_bindings[].package_id; a continuing condition is also readable as an indicator through get_media_buys. The seller may instead return input-required before consuming the proposal. Warnings never appear on failed or submitted arms. An unexpired committed proposal cannot be rejected merely because its reserved inventory was sold elsewhere. Once expires_at passes, the hold lapses and the seller returns PROPOSAL_EXPIRED; the buyer must request and finalize a fresh proposal.