How do I give an AI agent a tamper-evident receipt for an action it took?

Hash the action record — the tool called, the inputs, the outputs, the timestamp, and the agent's identity — at the moment it happens, then anchor that fingerprint to a public blockchain. The result is a receipt anyone can independently verify later, and any change to the recorded action becomes detectable. LedgerProof issues these hash-only receipts, cryptographically anchored to the public chain, so an autonomous agent's actions and handoffs carry proof that stands up without trusting the operator that produced them.

Why autonomous agents need receipts, not just logs

A core rule of production agent design is to audit every call: log inputs, outputs, timestamp, and agent ID for each tool invocation. But an audit trail is only as trustworthy as its weakest guarantee — and a log written to storage the operator controls can be edited or regenerated after the fact. As agents gain autonomy and hand work to one another, the question "what exactly did this agent do, and when?" becomes something a counterparty, an auditor, or the next agent needs to answer without taking your word for it.

What belongs in an agent action receipt

Field	Why it's in the receipt
Agent identity	Which agent (and version) took the action
Action / tool called	The specific capability invoked — one tool, one job
Input hash	Binds the receipt to exact inputs, without exposing them
Output hash	Binds the receipt to exact outputs, without exposing them
Timestamp	When it happened — anchored so it can't be backdated
Parent / handoff reference	Links the action into the chain of custody across agents

Hashing the inputs and outputs is what makes this safe to receipt at all: the receipt proves exactly what happened while the sensitive content stays inside your systems.

Verifiable handoffs between agents

In a multi-agent system, the dangerous failure mode is implicit trust — Agent B acting on Agent A's output as if it were ground truth. A tamper-evident receipt turns a handoff into something checkable: before acting, the receiving agent (or a human gate) verifies the upstream receipt against the public chain to confirm the action and its outputs existed, unaltered, at the stated time. Untrusted-until-validated becomes enforceable, not aspirational.

How LedgerProof issues the receipt

Wrap the call. The SDK wraps a tool call or handoff and computes the SHA-256 fingerprint of the action record locally — negligible overhead.
Batch and anchor. Fingerprints are folded into daily RFC-9162 Merkle roots and anchored to the public chain via a public-ledger transaction, so cost and latency don't scale per action.
Verify independently. Any holder of the receipt re-checks it against the public chain with the open-source verifier — no account, no dependency on LedgerProof still running.

What this does and doesn't do. A LedgerProof receipt proves that an agent action, in a specific form, existed at a specific time and has not been altered since. It does not prove the action was correct, authorized, or safe — only that it happened as recorded. It is evidence for a human or auditor to judge, not a verdict. Proofs are tamper-evident, not tamper-proof.

Frequently asked questions

What should an AI agent action receipt contain?

At minimum: the agent's identity, the tool or action invoked, a hash of the inputs, a hash of the outputs, a timestamp, and a reference to the parent action or handoff. Hashing the inputs and outputs keeps sensitive content private while still binding the receipt to exactly what happened.

Why isn't a normal agent log tamper-evident?

A normal log is written to storage the operator controls and can be edited or regenerated later. It cannot prove to a downstream agent, an auditor, or a counterparty that the recorded action happened exactly as shown, at that time. Anchoring each action's fingerprint to a public blockchain makes any later change detectable and independently checkable.

Can a downstream agent verify an upstream agent's receipt before trusting it?

Yes — that is the point of a verifiable handoff. Treat subagent output as untrusted until validated: the receiving agent (or a human reviewer) can check the upstream receipt against the public chain to confirm the action and its outputs existed unaltered before acting on them.

Does receipting agent actions add latency or send data to a third party?

Fingerprinting is a local SHA-256 hash with negligible overhead, and it is hash-only — the inputs and outputs never leave your systems. Fingerprints are batched into daily Merkle roots, so anchoring cost and latency do not scale per action.

Wrap your first agent call → Verify a real receipt yourself

Related: EU AI Act Article 50 evidence · IETF Internet-Draft (SCITT receipts) · LedgerProof SDK

Last updated 2 July 2026 · LedgerProof