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x402 Signature Service — Electronic Signature Request
x402
x402 Signature Service — Electronic Signature Request is a paid API for AI agents from x402-signature-service.onrender.com, paid per call via x402, $0.5/call, status unknown (last checked 2026-09-15).
Sends a PDF document to a named email recipient for electronic signature, returning a tracking ID, status URL, and one-time access token.
Price / call$0.5
Success—
StatusUnknown
How this service works
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.
Output
Returns a JSON object containing a unique signature request ID, the signer's name and partially masked email, the current status (e.g. 'sent'), creation and expiration timestamps, a URL to poll for status updates, a one-time plain-text bearer access token for subsequent API calls, and the document name.
Example use cases
Client contract signing automation
“Send my consulting contract PDF at https://docs.mycompany.com/consulting-contract.pdf to John Smith at john.smith@clientco.com for his e-signature — include the message 'Please sign this to kick off our engagement' and set it to expire in 7 days.”
NDA collection before onboarding
“I need Sarah Connor at sarah@startup.io to sign our NDA before her onboarding call tomorrow. Can you send her the NDA from https://hr.mycompany.com/nda.pdf with the note 'Please sign before your onboarding session' and give her 3 days to complete it?”
Freelancer invoice approval
“Send the project scope agreement at https://files.freelance.io/scope-2024.pdf to my client Mike Torres at mike@torresco.com — title it 'Project Scope Agreement', add the message 'Kindly sign to confirm project terms', and set it to expire in 5 days.”
Technical details
Endpoint
GEThttps://x402-signature-service.onrender.com/v1/signature-requestsWhen to prefer
Choose this endpoint when you need to send a single PDF document to a single recipient for electronic signature and want a pay-per-call, no-subscription model billed in USDC via the x402 protocol. Ideal for AI agents that need to automate contract or agreement signing without setting up a full e-signature SaaS subscription. Not suitable for bulk multi-recipient signing, non-PDF formats, or when you need advanced signing workflows (field placement, multi-party ordering).
Side effects
- Invalid or unreachable PDF URL returns an error (document fetch failure)
- PDF exceeds 5 MB size limit causes rejection
- Invalid signer email format fails schema validation
- Both documentUrl and documentBase64 provided simultaneously causes conflict error
- Neither documentUrl nor documentBase64 provided causes missing document error
- Payment of $0.50 USDC not included or insufficient triggers 402 Payment Required
- Expired or missing x402 payment header blocks request
- expiresInDays outside 1–30 range fails validation
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| signer | object | |
| message | string | Optional message included in the signature request email |
| documentUrl | string | HTTPS URL of the PDF to sign (max 5 MB). Provide either documentUrl OR documentBase64. |
| documentName | string | Human-readable document title shown to the signer |
| expiresInDays | integer | Days until the signature request expires |
| documentBase64 | string | Base64-encoded PDF (max 5 MB decoded). Provide either documentUrl OR documentBase64. |
| externalReference | string | Optional caller-side reference id, echoed back in responses |
Output
Schema · Response
{
"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"
}
}Tags
x402
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