{"uid":"cap_Whx3vH-DSHsv4dLDVZeEk","slug":"x402-signature-service-e-signatures-for-ai-agents-8bb00555","name":"x402 Signature Service — E-Signatures for AI Agents","description":"Pay-per-call API (x402, $0.50 USDC on Base): send one PDF to one email recipient for simple electronic signature, track status, download the signed PDF.","url":"https://signx402.com/v1/signature-requests","method":"GET","headers":{},"bodySchema":{"type":"object","properties":{"signer":{"type":"object","required":["name","email"],"properties":{"name":{"type":"string","maxLength":120,"minLength":1},"email":{"type":"string","format":"email"}}},"message":{"type":"string","maxLength":2000,"description":"Optional message included in the signature request email"},"documentUrl":{"type":"string","description":"HTTPS URL of the PDF to sign (max 5 MB). Provide either documentUrl OR documentBase64."},"documentName":{"type":"string","maxLength":150,"minLength":1,"description":"Human-readable document title shown to the signer"},"expiresInDays":{"type":"integer","default":14,"maximum":30,"minimum":1,"description":"Days until the signature request expires"},"documentBase64":{"type":"string","description":"Base64-encoded PDF (max 5 MB decoded). Provide either documentUrl OR documentBase64."},"externalReference":{"type":"string","maxLength":200,"description":"Optional caller-side reference id, echoed back in responses"}}},"responseSchema":{"type":"json","example":{"id":"sigreq_1f4a9c2b7d3e8a01","signer":{"name":"Anna Müller","email":"a***@example.com"},"status":"sent","createdAt":"2026-07-19T15:00:00Z","expiresAt":"2026-08-02T15:00:00Z","statusUrl":"https://your-api.example.com/v1/signature-requests/sigreq_1f4a9c2b7d3e8a01","accessToken":"sec_… (plain-text bearer token, shown exactly once)","documentName":"Service Agreement"}},"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.5","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":"$0.5/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.5","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.5","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_iPMdc7-Qccy3oUz3_htfg","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.5","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Sends a PDF document to an email recipient for electronic signature, returns a tracking token and status URL, and enables status polling and signed PDF retrieval.","exampleAgentPrompt":"Send our NDA PDF (https://docs.mycompany.com/nda.pdf) to Jordan Lee at jordan.lee@acmecorp.com for electronic signature — title it 'Mutual NDA', include a note saying 'Please review and sign by end of week', and set it to expire in 7 days.","exampleUseCases":[{"title":"Contractor agreement signing","prompt":"Send this contractor agreement PDF at https://files.mycompany.com/contractor-agreement.pdf to Sarah Chen at sarah.chen@freelancer.io for her signature — call it 'Contractor Services Agreement', add the message 'Hi Sarah, please sign at your earliest convenience', and give her 10 days before it expires."},{"title":"Client onboarding signature","prompt":"I need a new client to sign our onboarding terms — send the PDF from https://legal.mybiz.com/onboarding-terms.pdf to Marcus Webb at m.webb@clientco.com, title it 'Client Onboarding Agreement', and let them know they have 14 days to sign it."},{"title":"Vendor NDA collection","prompt":"Request a signature on our standard vendor NDA — the PDF is base64-encoded, signer is Priya Sharma at priya@vendorcorp.net, name the document 'Vendor Non-Disclosure Agreement', include the message 'Please sign before our kickoff call', and set expiry to 5 days."}],"resultDescription":"Returns a JSON object with a unique signature request ID (e.g. sigreq_…), signer details (name and masked email), current status ('sent'), creation and expiry timestamps, a statusUrl for polling the request status, a one-time plain-text access token for downstream management calls, and the document name.","failureModes":["Invalid or unreachable documentUrl returns an error (PDF could not be fetched)","PDF exceeds 5 MB size limit causes rejection","Invalid signer email format triggers validation error","Missing required fields (signer name, email, document source) returns 400-level error","Payment not completed via x402 protocol results in 402 Payment Required response","Both documentUrl and documentBase64 provided simultaneously may cause conflict error","expiresInDays outside range 1–30 triggers validation error"],"whenToPreferThis":"Choose this endpoint when an AI agent needs to automate the e-signature step of a document workflow on a pay-per-call basis with no subscription required — particularly suited for agentic pipelines where cost predictability ($0.50 USDC flat per request) matters and the use case is one PDF to one email recipient. Prefer this over subscription-based e-sign platforms when volume is low or unpredictable, or when the agent must handle payment natively via the x402 protocol on Base.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-15T06:33:58.209Z","isFirstParty":false}