How It Works

A visual guide to the core mechanics of the Agent Receipt Protocol.

What’s in a receipt

Every Agent Receipt is a W3C Verifiable Credential recording a single agent action. It captures what happened, who authorized it, whether it succeeded, and where it sits in a tamper-evident chain.

The four required sections — principal, action, outcome, and chain — are always present. Optional sections like intent (why the agent acted) and delegation (who delegated the task) add context when available.

How receipts are signed

Before a receipt can be trusted, it needs a cryptographic signature proving the issuer created it and the contents haven’t been altered.

1. Start with the receipt fields (everything except proof)
2. Serialize to RFC 8785 canonical JSON — deterministic byte ordering
3. Sign the canonical bytes with the issuer’s Ed25519 private key
4. Encode the signature as z-prefixed base58btc and attach as proof.proofValue

The same canonical bytes are also SHA-256 hashed to produce the link for the next receipt in the chain.

How receipts chain

Each receipt includes the SHA-256 hash of the previous receipt’s canonical form. This creates a tamper-evident sequence — modifying any receipt breaks the chain from that point forward.

All receipts in a chain share the same chain_id and issuer.id. A chain must have exactly one issuer — when an agent delegates work, the delegated agent starts a new chain.

How delegation works

When Agent A delegates a task to Agent B, Agent B creates its own receipt chain and links back to Agent A’s chain using the delegation field.

Key rules:

• A chain must have a single issuer — Agent B cannot add receipts to Agent A’s chain
• The delegated chain’s first receipt carries a delegation field with parent_chain_id, parent_receipt_id, and delegator.id
• Both chains share the same principal — the human who authorized the work doesn’t change across delegation

For the full field reference, see the Agent Receipt Schema. For verification algorithms, see Receipt Chain Verification.