> ## Documentation Index
> Fetch the complete documentation index at: https://docs.adcontextprotocol.org/llms.txt
> Use this file to discover all available pages before exploring further.

# accept_proposal

> Accept a committed proposal to create, amend, or cancel a MediaBuy.

`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`](https://adcontextprotocol.org/schemas/3.0.23/media-buy/accept-proposal-request.json)

```json theme={null}
{
  "idempotency_key": "550e8400-e29b-41d4-a716-446655441011",
  "account": { "account_id": "account_123" },
  "proposal_id": "proposal_committed_456",
  "proposal_terms_digest": "sha256:AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
}
```

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`](/dist/docs/3.0.23/media-buy/task-reference/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`](/dist/docs/3.0.23/building/verification/compliance-catalog#error-code-proposal-expired); the buyer must request and finalize a fresh proposal.