{"uid":"cap_irQwTw6FLiPbuNzgYz4XN","slug":"evm-nonce-replace-check-406149c6","name":"EVM Nonce Replace Check","description":"EVM Nonce Replace Check: EVM Nonce Replace Check checks whether a proposed nonce targets a caller-supplied pending nonce from bounded caller-supplied values without an external provider. Call EVM Nonce Replace Check before signing, submitting, replacing, or accepting an EVM/Base transaction assembled from caller-owned data. Returns normalized transaction evidence, calculated budget or shape findings, and a fail-closed preflight status for EVM Nonce Replace Check as versioned deterministic JSON.…","url":"https://api.delx.ai/api/v1/x402/evm-nonce-replace-check","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"pending_nonces":{"type":"array","items":{"type":"integer"},"maxItems":256,"description":"Pending Nonces supplied to EVM Nonce Replace Check; used only for this bounded calculation and processed in memory without retention."},"proposed_nonce":{"type":"integer","description":"Proposed Nonce supplied to EVM Nonce Replace Check; used only for this bounded calculation and processed in memory without retention."}}},"responseSchema":{"type":"json","example":{"result":{"proposed_nonce":11,"targets_pending":true},"schema":"delx/util-evm-nonce-replace-check/v1","status":"pass","evidence":{"retained":false,"input_sha256":"a3ab4cbc105327ec6bf99174fcfd83de2a8605ff927d8cd849aed39cba23d03e","external_calls":0},"operation":"evm_preflight:evm_nonce_replace_check"}},"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.001","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.001/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.001","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.001","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_Z-Vds7966KoiltBKAofw0","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.001","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Checks whether a proposed EVM transaction nonce targets any pending nonces in a list, enabling pre-flight nonce replacement safety validation.","exampleAgentPrompt":"Before I submit my next Ethereum transaction, check if proposed nonce 11 would replace any of these pending nonces [8, 9, 10, 11] in my queue.","exampleUseCases":[{"title":"Pre-flight nonce check before transaction broadcast","prompt":"I'm about to broadcast an EVM transaction with nonce 42 — can you check if that nonce would replace any of the currently pending nonces [40, 41, 42, 43] in my wallet queue before I send it?"},{"title":"Agent transaction queue conflict detection","prompt":"My autonomous trading agent has pending nonces [5, 6, 7] queued up. Check whether using proposed nonce 6 would collide and replace one of those pending transactions."},{"title":"Nonce safety validation for gas bump retry","prompt":"I'm trying to speed up a stuck transaction by resubmitting with nonce 15. My pending nonces are [14, 15, 16] — verify whether nonce 15 is actually targeting a pending transaction before I proceed."}],"resultDescription":"Returns a JSON object with the proposed nonce value, a boolean flag (targets_pending) indicating whether it matches any pending nonce, the operation name (evm_preflight:evm_nonce_replace_check), pass/fail status, and evidence metadata including input hash, retention status (always false), and external call count (always 0).","failureModes":["Invalid pending_nonces array (non-integer elements or exceeds 256 item limit) returns validation error","Missing required proposed_nonce field returns schema error","Malformed JSON body returns 400 bad request","Payment not included or invalid x402 payment header returns 402 Payment Required"],"whenToPreferThis":"Use this endpoint when an AI agent or automated system needs to verify whether a proposed EVM transaction nonce would replace an existing pending transaction before submission, especially in high-throughput or automated transaction pipelines where nonce collisions can cause unintended transaction replacement. Prefer this over manual nonce management when building safe transaction queues or retry logic for stuck transactions.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-15T07:11:43.947Z","isFirstParty":false}