Set x402 spending limits for AI agents
Use per-payment caps, approval thresholds and a caller-owned daily spending ledger before signing.
Apply a policy before every signature
Preflight supports max_per_payment_usd, hold_above_usd and daily_cap_usd. The live defaults are a $1 per-payment maximum, a hold above $0.25, and a $25 daily cap. Supply your own rules for your application rather than treating these defaults as financial advice.
The daily ledger belongs to your client
Send context.spent_today_usd with an accurate total. SpendPreflight does not retain request bodies or maintain an authoritative shared daily spending balance. Reserve budget atomically across concurrent agents, include screening fees in your own budget, and reconcile successful settlements. Passing zero on every call defeats the daily limit.
Restrict what can be paid
Use allowed_networks, usdc_only, domain and payTo allowlists or blocklists, and strict_allowlist as appropriate. The service returns allow, hold or block; your wallet hook must reject hold and block. Revalidate a changed challenge instead of reusing approval for a different price or payee.
Integrate without a subscription
POST /v1/preflight is $0.02 per call in Base USDC. The published npm spendpreflight client also supports local policy checks without an API call. Remote screening is an explicit option with its own fee; it does not authorize the merchant payment. Three free HTTP/MCP trial calls per IP per UTC day are shared across tools.
Connect your payment client
Tested fetch, axios, Vercel and OpenAI Agents examples · Live default rules · OpenAPI
We operate SpendPreflight. Scout discovery and seller monitoring remain staging-only; these guides describe the live check/preflight service.
Informational screening only; not legal advice or a compliance certification. Trust and limitations · Privacy