Payment Verification Is Not Payment Authorization

Existing payment infrastructure can verify whether a payment is valid. It may not determine whether an autonomous agent should make that payment.

x402Shield evaluates whether an agent payment is permitted before any signing capability is reached.

How It Works

x402Shield sits between autonomous agent actions and payment execution, converting probabilistic model output into deterministic security decisions.

AGENT RUNTIME
Agent Action Proposal
Probabilistic output
Canonical Payment Intent
Normalized parameters
x402SHIELD SECURITY CORE
Deterministic Policy Engine
IDENTITYWAITING
CONTEXTWAITING
RECIPIENTWAITING
BUDGETWAITING
POLICY DECISION
WAITING
EXECUTION BOUNDARY
Restricted Signer
Key custody execution
x402 Payment
Final transaction

Core Security Controls

Payment Intent Validation

Normalize and validate payment actions before they reach the signing boundary.

Recipient and Network Policies

Restrict recipients, assets, chains and value limits through owner-defined rules.

Request-Bound Authorization

Bind authorization to the intended request, resource, amount and expiration.

Replay and Concurrency Protection

Prevent proofs and authorizations from being reused across parallel executions.

Prompt-Injection Risk Signals

Treat untrusted content and tool output as security signals, not final decisions.

Restricted Wallet Signing

Keep arbitrary signing capabilities outside the autonomous agent runtime.

Designed for the Agent Payment Boundary

x402Shield is being designed as an inline enforcement layer rather than a custodial wallet or general-purpose payment gateway.

Agent / MCP Client
↓
x402Shield
↓
Restricted Signer
↓
x402 API / Payment Network

Test x402Shield Against a Real Agent Payment Flow

We are looking for teams building x402 clients, autonomous agents, agent wallets and paid MCP services.