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SpendPreflight Listing Guard
x402
SpendPreflight Listing Guard is a paid API for AI agents from api.spendpreflight.com, paid per call via x402, $0.05/call, status unknown (last checked 2026-10-28).
Validates marketplace listings for AI agent safety risks — detecting prompt injections, embedded URLs, tool call abuse, invisible Unicode, and anomalous pricing — returning a risk score, flagged spans, and rewrite suggestions.
Price / call$0.05
Success—
StatusUnknown
How this service works
Bazaar Listing Guard: CDP technical validation plus a bounded heuristic metadata screen for agent-directed instructions, embedded URLs, tool calls, invisible Unicode, long fields and prices above 100x a fresh Scout category median. Returns riskScore, flagged spans and rewrite suggestions. Not Coinbase policy certification or guaranteed detection. Public HTTPS only; no target payment or request bodies stored.
Output
Returns a riskScore (numeric), a list of flagged spans identifying suspicious content regions (e.g. invisible Unicode, embedded URLs, tool calls, prompt injection patterns, oversized fields), and rewrite suggestions to remediate the flagged issues. Does not store request bodies or target payment details.
Example use cases
Pre-purchase listing safety scan
“Before buying that item from the Bazaar marketplace, scan the listing at https://bazaar.example.com/items/456 via GET and tell me if there's anything suspicious — hidden instructions, weird Unicode, or a price way above the category median.”
Detecting prompt injection in agent workflow
“My agent is about to follow instructions from a listing at https://store.example.com/product/789 — can you do a POST preflight check on it first and flag any embedded tool calls or injected agent instructions before it proceeds?”
Anomalous price alert before payment
“Check the listing at https://marketplace.example.com/offers/321 with a HEAD request through Listing Guard — I specifically want to know if the price is more than 100x the Scout category median and whether there are any rewrite suggestions.”
Technical details
Endpoint
POSThttps://api.spendpreflight.com/listing-guard?utm_source=zero.xyzWhen to prefer
Use this endpoint when an AI agent is about to act on, purchase, or process a marketplace listing and you need a bounded technical safety screen — specifically for prompt injection, embedded URLs, invisible Unicode, tool call abuse, and price anomalies. Prefer this over generic content moderation APIs when the threat model is agent-directed manipulation (adversarial listings targeting AI agents). Not a substitute for full Coinbase policy certification or sanctions screening (use sibling SpendPreflight endpoints for payment risk).
Side effects
- Invalid or unreachable URL returns an error — ensure the URL is publicly accessible via HTTPS
- Unsupported HTTP method (outside GET, HEAD, POST) returns a validation error
- Rate limiting or payment failure via x402 may prevent the call from completing
- Listings with no detectable issues still return a response but with low riskScore — not a guarantee of safety
- Scout category median data may be stale, affecting price anomaly detection accuracy
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| url | string | |
| method | string |
Tags
x402
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