x402-signature-service

x402 · $0.50 USDCBasee-signature

Agent-native API that closes a critical capability gap: an AI agent sends a PDF to a human for signature, tracks progress, and downloads the signed document — fully autonomously, paid per call via x402.

⚠️ Disclaimer: This MVP facilitates simple electronic signatures through the configured signature provider. Users are responsible for determining whether this signature type is appropriate for their document, jurisdiction, and use case.

Usage

POST https://signx402.com/v1/signature-requests   # 402 + payment requirements (x402)
# pay $0.50 USDC on Base, retry with payment header
# -> 201 { "id": "sigreq_…", "accessToken": "sec_…", "statusUrl": "…" }

GET  https://signx402.com/v1/signature-requests/<id>            # Authorization: Bearer sec_…
GET  https://signx402.com/v1/signature-requests/<id>/document   # signed PDF once completed

Free machine-readable schema & examples: /v1/schema · LLM tool definition: /agent-tool.json · OpenAPI: /docs

Why agents use this

Human-in-the-loop, agent-operated: the signer gets a normal e-mail + browser signing page (Documenso); the agent keeps full control via API.
Secure by design: SSRF-guarded document fetching, one-time bearer tokens (only hashes stored), masked e-mail addresses in logs.
Private: PDFs are processed in memory and never written to logs; completed requests are purged automatically.