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An update proposal is a pending change to a media buy that awaits resolution by the sales agent. It moves from PENDING to either APPROVED or REJECTED. While a proposal is PENDING, you can poll its status or cancel it; once resolved, it is terminal. Buyer agents using the api_call MCP tool can poll with get_update_proposal and withdraw a pending proposal with cancel_update_proposal, passing the proposal ID returned by update_campaign as pathParams.proposalId. Cancellation resolves the pending Interchange proposal as REJECTED with rejectionReason: "cancelled_by_buyer", retains a safety record so a later callback cannot apply it locally, and releases the one-pending-update gate. It does not recall a request that Interchange already dispatched to the seller; contact the seller/operator when the upstream task itself must be withdrawn. Poll the proposal until status leaves PENDING. When a proposal is REJECTED, read rejectionReason for the cause. To withdraw a change before the agent acts, cancel it. All requests use the base URL https://api.interchange.io/api/v2/buyer and a Authorization: Bearer $SCOPE3_API_KEY header.

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Task Reference

Get update proposal

GET /update-proposals/:id — poll resolution status

Cancel update proposal

DELETE /update-proposals/:id — withdraw a pending proposal

All update proposal tasks

Per-operation reference