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Idempotency Replay Guard
x402
Idempotency Replay Guard is a paid API for AI agents from phion.systems, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-14).
Detects whether reuse of an idempotency key is a safe replay of a prior request or a conflicting misuse that should be rejected
Price / call$0.002
Success—
StatusUnknown
How this service works
Detect safe replays and conflicting reuse of an idempotency key
Output
Returns a classification of the idempotency key reuse as either a safe replay (identical request repeated) or a conflicting reuse (same key, different parameters), along with relevant flags and evidence to guide the caller's decision on whether to proceed, reject, or escalate.
Example use cases
Safe payment retry verification
“I'm about to retry a failed payment with idempotency key 'txn-7f3a-9812' — can you check whether this is a safe identical replay or if the key was already used for a different amount or recipient?”
Detecting conflicting key reuse in agent loop
“My agent loop may have submitted the same tool call twice with key 'agent-op-5521' but with slightly different inputs — can you check if that's a safe replay or a conflict I need to resolve?”
Audit idempotency violations before reconciliation
“Before I reconcile today's transactions, flag any idempotency keys that were reused with conflicting payloads rather than safe identical retries — here's the key list from today's run.”
Technical details
Endpoint
POSThttps://phion.systems/v1/paid/trust/idempotency-replay-guardWhen to prefer
Use this endpoint when an agent or system is about to retry an operation and needs to verify whether the idempotency key is being reused safely (identical request) or dangerously (different payload or intent). Especially valuable in x402 payment flows, multi-step agentic pipelines, or any workflow where duplicate execution has financial or state consequences. Prefer this over ad-hoc key comparisons when you need a structured, policy-driven verdict rather than a simple equality check.
Side effects
- Insufficient key or payload context provided — returns validation error
- Key not found in prior request history — cannot determine replay vs. conflict
- Ambiguous payload diff — partial match may yield inconclusive classification
- Malformed idempotency key format — rejected at input validation
- Service unavailable or timeout — caller should not assume safe replay
Input
Schema · Request body
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"type": "object"
}Tags
x402
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