How do I send a document for e-signature via API?

Make a single POST request to https://signb.ee/api/v1/send with your document content (markdown or PDF URL), recipient name, and recipient email. The recipient receives a signing link by email. Both parties get a SHA-256 certified PDF when signing is complete.

Does Signbee require an SDK?

No. Signbee is a single REST endpoint. Use fetch in JavaScript, requests in Python, or any HTTP client. No SDK, no client library, no build step required.

Is the Signbee API free?

Yes. The free tier includes 5 legally binding documents per month. No credit card required. Paid plans start at $9/month for 100 documents.

Can AI agents use Signbee?

Yes. Signbee offers three integration methods for AI agents: a REST API for direct HTTP calls, an MCP server (npx signbee-mcp) for Claude/Cursor/Windsurf, and an llms.txt file for AI discoverability.

API Reference

Signbee is a document signing API built for AI agents. One API call sends a document for two-party e-signing — both parties sign, both receive a SHA-256 certified PDF.

No SDK, no client library, no build step. Use the native HTTP client in any language — fetch in JavaScript, requests in Python, http.Client in Go. See 20+ framework examples.

Base URL

https://signb.ee

Format

JSON in, JSON out

OpenAPI Spec

/openapi.json

Endpoints

4 total

Authentication POST /send POST /generate GET /documents DELETE /documents Document Lifecycle Rate Limits MCP Server Errors

Authentication

Signbee supports two modes. You can start using the API immediately without an API key — no signup required.

With API key Recommended

Sender is pre-verified. Recipient gets the signing email immediately. Best for automated agent workflows and production integrations.

Without API key Quick start

Sender verifies via email OTP first. No signup or account needed. Good for testing and one-off documents.

Header (when using API key)

Authorization: Bearer YOUR_API_KEY

Get your API key at signb.ee/dashboard — free tier includes 5 documents per month.

Endpoints

POST/api/v1/send

Send a document for two-party e-signing. Provide either markdown or a PDF URL.

Auth: Optional — Bearer token or email OTP

Required fields

recipient_name— Full name of the recipient

recipient_email— Email address of the recipient

markdown— Document content (min 10 chars, max 50KB)

Or use pdf_url instead of markdown to send an existing PDF

Required without API key

sender_name— Full name of the sender

sender_email— Email address of the sender

Optional fields

title— Document title (auto-extracted from first heading if omitted)

expires_in_days— Days until signing link expires (default: 7, max: 30)

pdf_url— URL to an existing PDF (alternative to markdown)

curl

curl -X POST https://signb.ee/api/v1/send \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -d '{
    "markdown": "# Mutual NDA\n\nThis agreement...",
    "recipient_name": "Bob Smith",
    "recipient_email": "bob@acme.com"
  }'

JavaScript (fetch)

const res = await fetch("https://signb.ee/api/v1/send", {
  method: "POST",
  headers: {
    "Content-Type": "application/json",
    "Authorization": "Bearer YOUR_API_KEY",
  },
  body: JSON.stringify({
    markdown: "# Mutual NDA\n\nThis agreement...",
    recipient_name: "Bob Smith",
    recipient_email: "bob@acme.com",
  }),
});
const data = await res.json();
console.log(data.document_id);

Python (requests)

import requests

res = requests.post(
    "https://signb.ee/api/v1/send",
    headers={"Authorization": "Bearer YOUR_API_KEY"},
    json={
        "markdown": "# Mutual NDA\n\nThis agreement...",
        "recipient_name": "Bob Smith",
        "recipient_email": "bob@acme.com",
    },
)
print(res.json()["document_id"])

Response (with API key)

{
  "document_id": "cmm...",
  "status": "pending_recipient",
  "sender": "Alice Chen",
  "recipient": "Bob Smith",
  "expires_at": "2026-04-19T12:00:00.000Z"
}

POST/api/v1/generate

Generate a PDF from markdown without initiating a signing flow. Useful for previewing documents before sending.

Auth: Not required

Required fields

markdown— Document content (min 10 chars, max 50KB)

curl

curl -X POST https://signb.ee/api/v1/generate \
  -H "Content-Type: application/json" \
  -d '{"markdown": "# Invoice\n\nAmount: $500"}'

Response

{
  "document_id": "cmm...",
  "url": "https://signb.ee/view/cmm...",
  "expires_at": "2026-04-16T12:00:00.000Z"
}

GET/api/v1/documents/{id}

Get the current status, signing URLs, and PDF links for a document. Use this to poll for completion.

Auth: Required — Bearer token

curl

curl https://signb.ee/api/v1/documents/cmm... \
  -H "Authorization: Bearer YOUR_API_KEY"

Response

{
  "document_id": "cmm...",
  "status": "pending_recipient",
  "title": "Mutual NDA",
  "sender": { "name": "Alice Chen", "signed_at": "..." },
  "recipient": { "name": "Bob Smith", "signed_at": null },
  "original_pdf_url": "...",
  "signed_pdf_url": null,
  "signing_url": "https://signb.ee/sign/...",
  "expires_at": "...",
  "created_at": "..."
}

DELETE/api/v1/documents/{id}

Revoke a pending document. The signing link becomes invalid immediately.

Auth: Required — Bearer token

Response

{
  "success": true,
  "message": "Document revoked. The signing link is no longer valid."
}

Document Lifecycle

Every document moves through a predictable state machine. Poll GET /api/v1/documents/{id} to track progress.

Status	Meaning	Next
draft	PDF generated, no signing flow started	—
pending_sender	Awaiting sender OTP verification	pending_recipient
pending_recipient	Sender signed, awaiting recipient	signed
signed	Both parties signed — `signed_pdf_url` available	Terminal
expired	Signing link expired before completion	Terminal
revoked	Cancelled via DELETE — signing link invalidated	Terminal

The SHA-256 signing certificate is generated when status moves to signed. Both parties receive the certified PDF by email automatically.

How the Signing Flow Works

01Agent calls POST /api/v1/send with document content and party details
02With API key: sender is pre-verified, recipient gets signing email immediately
03Without API key: sender verifies via OTP, then recipient gets signing email
04Recipient clicks link, reviews the document, and signs
05Both parties receive the signed PDF with SHA-256 certificate via email

Agent Integrations

Beyond the REST API, Signbee exposes e-signing to AI agents through two additional protocols. For the full context on agent discoverability, see The Multi-Protocol Future.

MCP Server

Works with Claude Desktop, Cursor, Windsurf, and any MCP-compatible client. Exposes a send_document tool that AI agents can call without writing API code.

{
  "mcpServers": {
    "signbee": {
      "command": "npx",
      "args": ["-y", "signbee-mcp"],
      "env": { "SIGNBEE_API_KEY": "YOUR_API_KEY" }
    }
  }
}

npm: signbee-mcp · Guide: 2-minute setup

llms.txt

Machine-readable product description for AI agents. Tells LLMs what Signbee can do, how to call the API, and where to find docs — without scraping.

signb.ee/llms.txt · What is llms.txt?

Direct API

Call the REST API from any language. No SDK needed — just HTTP + JSON. See 20+ framework guides with copy-paste examples.

OpenAPI spec: signb.ee/openapi.json

Rate Limits

Plan	Documents / month	Email rate
Free	5	1 per minute
Pro ($9/mo)	100	10 per minute
Business ($29/mo)	Unlimited	30 per minute

When you hit a rate limit, the API returns 429 with a Retry-After header. Document limits reset on the 1st of each month.

Error Codes

Code	Meaning	Action
400	Missing or invalid fields	Check request body
401	Invalid API key	Regenerate at /dashboard
403	Plan limit reached or unauthorized	Upgrade plan or wait for reset
429	Email rate limit exceeded	Wait for Retry-After header
503	Email service temporarily unavailable	Retry after 30s

All error responses return JSON with an error field:{"error": "description"}

20+ Framework Guides Document Templates Glossary Free API Guide AI Agent Signing Best E-Signature APIs

Questions?

hello@signb.ee

Last updated: April 2026