The seven-field receipt skeleton is a solid foundation. The trickiest gap in practice is bridging these receipts with authorization: proving a tool call ran is useful, but a counterparty releasing payment needs to know the receipt was issued by an agent authorized to spend that amount. Thats where coupling receipts with agent identity and a capability model becomes critical. An issuer public key alongside the receipt fields would let any verifier check authorization without trusting the transport layer.
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