# Tereno Transaction Intent Guard

> Tereno Transaction Intent Guard is a paid API for AI agents from www.tereno.xyz, paid per call via x402, $0.05/call, status unknown (last checked 2026-10-13).

Simulates an unsigned Base transaction against live chain state and returns a safety verdict (allow/review/block) with reason codes, balance/allowance changes, gas estimate, and approval risk flags.

## Facts

- Endpoint: POST https://www.tereno.xyz/api/v1/capabilities/transaction.intent.guard/invoke?utm_source=zero.xyz
- Price: $0.05/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/tereno-transaction-intent-guard-cd58bde9
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_vL6_hWLkSCRudm63AclgC

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability tereno-transaction-intent-guard-cd58bde9 -d '<json body>'
```

Example prompt: Before I sign this transaction, run it through Tereno's guard — here's the raw unsigned tx hex: 0x02f8...abc. Tell me whether it's safe to sign, what token balances will move, whether there's any unlimited approval hiding in it, and whether the target contract has changed recently.

## When to prefer this

Choose this endpoint when you need a privacy-preserving, real-time safety verdict on a specific unsigned Base transaction before a user signs it — especially when you need to detect hidden unlimited approvals, confirm exact balance changes, or verify the target contract hasn't been swapped out. Prefer it over static contract analysis tools when you need live chain-state simulation rather than bytecode scanning, and over generic RPC simulation when you need a structured allow/review/block verdict with reason codes rather than raw trace output.

## Known failure modes

- Invalid or malformed transaction hex returns a 400-level error
- Transaction references a contract with no deployed code (returns block verdict with reason code)
- Simulation fails due to reverted call on-chain (returns block verdict with revert reason)
- Block validity window expires between simulation and signing (result flagged as stale)
- Unsupported transaction type or chain returns an error
- Payment not included or insufficient USDC triggers 402 payment required

## How this service works

Is this transaction safe to sign? Simulate an unsigned Base transaction against current chain state and get one verdict back: what the call does, the gas it burns, which balances and allowances move, and whether it hides an unlimited approval or a target that changed under you. Returns allow, review or block with reason codes, evidence and the block it stops being valid. Never cached, shared or resold: your unsigned transaction stays private to the wallet that paid for it.

## Output

Returns a verdict of 'allow', 'review', or 'block' along with structured reason codes explaining the decision, evidence of which token balances and ERC-20 allowances will change, estimated gas consumption, a flag if an unlimited approval is detected, a flag if the target contract has changed since the transaction was constructed, and the block number after which the simulation result is no longer valid.

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/tereno-transaction-intent-guard-cd58bde9/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from www.tereno.xyz](https://www.zero.xyz/host/www.tereno.xyz/llms.txt)