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Natural-language instructions are attractive because an agent can translate ‘pay this invoice if it matches the purchase order’ into a blockchain action. The danger appears when a broad request is converted into a signature that authorizes more than a person intended. EIP-712 helps represent structured fields rather than an opaque byte string, but readable presentation is not the same as safe delegated authority. A production design needs binding between human intent, machine plan, signed payload and final state. We outline a reproducible verification protocol, not an unsupported claim that one signing standard prevents fraud.
Translate a human instruction into narrow machine fields
An instruction like ‘buy a subscription’ is ambiguous about merchant, token, quantity, billing period and maximum spend. Before signing, convert it into structured fields: target contract, recipient, asset, amount cap, fee cap, chain, purpose and expiry. The system should show the original wording next to the exact executable meaning. The signer needs a chance to correct a misunderstood number or destination before the wallet is asked to approve anything.
EIP-712 provides a standard way to hash and sign typed data, with structures and domain information that wallet software can expose. Its specification does not guarantee that every wallet will render every field clearly. Product teams should therefore show their own plain-language confirmation and require an explicit acknowledgement for financial actions. The agent’s confidence score is not a substitute for a readable authorization.
Bind signatures to the proper domain
Domain separation includes context such as verifying contract and chain identifiers. This helps prevent a signature intended for one setting from being interpreted in another. However, EIP-712 explicitly says it does not include replay protection. Developers must provide their own nonce and consume it atomically, with a short validity period and a precise scope for permitted actions.
Test the same signature on the wrong chain, wrong contract, altered recipient and duplicated request. The contract or verification service should reject each case. If a backend merely trusts a user-facing confirmation screenshot, an attacker may be able to replay a structurally valid authorization in a different context. The verifier’s on-chain or authoritative state transition is what determines whether a nonce has been spent.
Handle task changes without silently widening consent
Agent plans evolve. A selected vendor may run out of inventory, a bridge may quote a different fee, or the recommended token may change. These are new decisions, not automatic permission to rewrite the signed terms. Establish tolerances in advance: a transaction may proceed within a signed price range, but a new vendor, asset or chain requires another explicit authorization. A good user experience communicates exactly which changes trigger a second signature.
Record the chain from original request to plan version to signed payload. When a task is retried, maintain the same intent identifier but create a new approval only if a material term changed. Avoid asking for broad unlimited allowances simply to make retries seamless. In complex workflows, the safest automation may be to stop and ask a person to resolve a meaningful ambiguity.
Separate credentials from spending authority
A verifiable credential can express an identity or qualification claim, such as a service provider’s accredited role, but it does not itself authorize the holder to spend funds. The W3C Verifiable Credentials Data Model v2.0, published as a Recommendation in May 2025, describes issuer, holder and verifier roles. Teams should validate relevant credentials and their status independently from the transaction signature.
For example, a credential may establish that an agent belongs to a vendor network, while the signed EIP-712 intent limits it to a single purchase at a defined price. Confusing these two layers makes privilege escalation easier: a verified business identity becomes a pretext for unlimited wallet authority. Keep authorization policy explicit, time-bound and revocable.
Test adversarial prompts and interface failures
Red-team tests should include a malicious web page that instructs the agent to change the payment recipient, a spreadsheet with hidden transfer instructions and a vendor name designed to mimic a legitimate counterparty. Measure whether the system propagates untrusted content into high-authority signature fields. Another test should deliberately hide a crucial field in the wallet UI to ensure the product confirmation still exposes it.
Classify each result as accepted within scope, rejected, or escalated for human approval. Do not grade the system solely by whether a blockchain transaction succeeded. Track unauthorized-intent acceptance, false approvals, correct refusals and time-to-human intervention. A low transaction-failure rate can coexist with poor consent quality when the system regularly executes the wrong intent successfully.
Operate a signed-intent evidence trail
For every high-impact task, retain the submitted instruction, normalized fields, simulation result, signature hash, verification timestamp, chain transaction hash, status, refund decision and approval-policy version. Sensitive personal data can remain off-chain, with public chains storing only necessary execution values or commitments. This makes post-incident reconstruction possible without publishing private user conversations.
Review a sample of completed tasks weekly. A useful metric is the percentage whose actual recipient, value and scope match the user’s confirmed intent, not merely the percentage with successful wallet signatures. EIP-7702 introduces important delegation possibilities for EOA behavior, but that increased flexibility makes precise approval design more—not less—important. The lasting product advantage is demonstrable fidelity between an instruction and the action that ultimately occurs.
