{"uid":"cap_xtZy3ipUMHKqqFjqiMvSG","slug":"x402-scheme-select-f84680d6","name":"X402 Scheme Select","description":"X402 Scheme Select: X402 Scheme Select selects the first buyer-supported payment scheme from challenge options from bounded caller-supplied values without an external provider. Call X402 Scheme Select before paying for or accepting an x402 or agent delivery assembled from caller-supplied challenge and result metadata. Returns contract-specific checks, normalized evidence, mismatch reasons, and an explicit acceptance or rejection status for X402 Scheme Select as versioned deterministic JSON. Pri…","url":"https://api.delx.ai/api/v1/x402/x402-scheme-select?utm_source=zero.xyz","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"schemes":{"type":"array","items":{"type":"string","maxLength":8192},"maxItems":256,"description":"Schemes supplied to X402 Scheme Select; used only for this bounded calculation and processed in memory without retention."},"supported_schemes":{"type":"array","items":{"type":"string","maxLength":8192},"maxItems":256,"description":"Supported Schemes supplied to X402 Scheme Select; used only for this bounded calculation and processed in memory without retention."}}},"responseSchema":{"type":"json","example":{"result":{"selected":"exact","supported":["exact"]},"schema":"delx/util-x402-scheme-select/v1","status":"pass","evidence":{"retained":false,"input_sha256":"a045739927a7259d237f0c405b73130cd2fb17caabdca6ce41cffff6ac4ff2ed","external_calls":0},"operation":"delivery_contract:x402_scheme_select"}},"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_d4zCPRQcGRsz262kspOj2","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":"Selects the first buyer-supported payment scheme from a list of x402 challenge scheme options, returning deterministic acceptance or rejection status.","exampleAgentPrompt":"From this list of x402 challenge schemes — ['exact/v1','evm/v1','base/v1'] — pick the first one that matches my supported schemes ['evm/v1','base/v1'] and tell me whether I should accept or reject the payment.","exampleUseCases":[{"title":"x402 payment flow scheme negotiation","prompt":"I'm about to pay for an agent delivery via x402 and the challenge returned these schemes: ['exact/v1','evm-base/v1','bitcoin/v1']. My wallet only supports ['evm-base/v1','solana/v1']. Which scheme should I use, and is this payment acceptable?"},{"title":"Agent delivery pre-authorization check","prompt":"Before my agent accepts this x402 payment request, check if any of the offered schemes ['exact/v1','erc20/v1'] are in my supported list ['erc20/v1','base/v1'] and give me a clear accept or reject decision."},{"title":"Multi-scheme compatibility filtering for buyer agent","prompt":"My buying agent received a challenge with schemes ['lightning/v1','evm/v1','exact/v1'] and supports only ['evm/v1']. Run the scheme selection and tell me which one was picked and any reasons if there's a mismatch."}],"resultDescription":"Returns a deterministic JSON object indicating which scheme was selected (the first buyer-supported scheme found in the challenge list), an explicit acceptance or rejection status, normalized evidence, mismatch reasons if no compatible scheme was found, and contract-specific check results — all versioned and computed in-memory without data retention.","failureModes":["No matching scheme found between offered and supported lists — returns rejection status with mismatch reasons","Empty schemes or supported_schemes arrays — may return rejection or empty selection","Malformed scheme strings or oversized arrays exceeding 256-item limit — may return validation error","Payment failure (insufficient USDC balance for $0.001 fee) — request not processed"],"whenToPreferThis":"Use this endpoint when implementing an x402 payment client or agent that needs to deterministically pick the correct payment scheme before authorizing or accepting a payment. It is the right choice when you have a list of schemes from a challenge response and a list of what your buyer supports, and you need a normalized, auditable selection decision without building the logic yourself. Prefer it over custom client-side logic when you need explicit mismatch reasons and a versioned JSON decision record for audit or debugging.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-20T07:14:39.808Z","isFirstParty":false,"canonicalSlug":"x402-scheme-select-f84680d6"}