Add E-Signatures to Flask

Quick start

1. Get an API key from signb.ee (free, no credit card)
2. Set SIGNBEE_API_KEY in your environment
3. Add the code below to your app

Flask example

from flask import Flask, request, jsonify
import requests

app = Flask(__name__)

@app.route("/send-contract", methods=["POST"])
def send_contract():
    data = request.get_json()
    response = requests.post(
        "https://signb.ee/api/send",
        headers={
            "Authorization": f"Bearer {os.environ['SIGNBEE_API_KEY']}",
            "Content-Type": "application/json",
        },
        json=data,
    )
    return jsonify(response.json())

What happens

1. Your app sends markdown or a PDF URL to Signbee
2. Signbee generates a PDF (if markdown) and emails the recipient a signing link
3. Recipient signs — both parties receive the signed PDF with SHA-256 certificate

Also works with AI agents

Install the MCP server to let Claude, Cursor, or Windsurf send documents directly:

npx -y signbee-mcp

Integration details

Flask is Python's lightweight web framework — minimal, flexible, and ideal for microservices and APIs. Adding e-signatures to Flask requires just a single route and the requests library.

Flask vs Django for e-signatures: Flask is better suited for microservices that handle specific tasks (like contract signing) independently. If e-signing is a small part of a larger application, Flask lets you build a focused signing service without the overhead of a full framework.

Blueprints: For larger Flask applications, organise your contract-related routes in a Blueprint. This keeps your signing logic separate from other application concerns and makes it easy to reuse across projects.

Flask-RESTful: If you're building a REST API with Flask, use Flask-RESTful or flask-smorest for structured API development. These libraries add request parsing, input validation, and automatic documentation generation.

Environment variables: Use python-dotenv to load SIGNBEE_API_KEY from a .env file during development. In production, set it via your deployment platform's environment configuration. Flask doesn't load environment variables automatically — you need python-dotenv or os.environ.

Gunicorn deployment: In production, run Flask behind Gunicorn with multiple workers. The Signbee API call is I/O-bound, so Gunicorn's async workers (gevent or eventlet) can handle many concurrent signing requests efficiently.

FAQs