REST API vs SDK: Which is Best for eSignature Integration

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Integrating eSignatures into your app can transform the way users sign contracts, allowing them to do so without leaving your platform. The question is: what’s the best way to integrate a service like BoldSign? Two popular tools dominate the scene: REST APIs and SDKs.

Think of a REST API as a universal mailbox. It’s accessible from anywhere with the right address. An SDK, on the other hand, is a pre-assembled toolkit, designed for specific tasks and requiring minimal setup.

In this guide, we’ll break down both options, compare their strengths, and show how BoldSign makes eSignature integration easy with both. Whether you’re building a customer portal or streamlining contracts, this guide will help you choose the best tool for your needs.

What is a REST API?

A REST API (representational state transfer application programming interface) is a standardized way for apps to communicate over the web using HTTP methods like GET, POST, PUT, and DELETE. These methods let you create, read, update, or delete records. REST APIs are stateless, meaning each request stands alone, and they use URLs to point to specific resources.

How It Works

1. Your app sends an HTTP request (e.g., POST to create a document) to a URL.

2. The server processes the request and returns data, usually in JSON or XML format.

Why Use REST APIs?

• Platform Independence: Works with any language that supports HTTP (e.g., Python, JavaScript).

• Scalability: Works well for large, distributed systems like microservices.

• Flexibility: Provides full control over requests and interactions.

What is an SDK?

An SDK (software development kit) is a collection of tools, libraries, documentation, and sample code designed to simplify building apps for a specific platform or service. SDKs wrap complex API calls into simple functions, saving you from writing repetitive code.

How It Works

1. Install the SDK: Add the SDK library to your project (e.g., via pip for Python).

2. Use Functions: Call prebuilt methods (e.g., send_document()) instead of crafting raw HTTP requests.

Why Use SDKs?

• Speed: Simplifies integration with ready-made functions.

• Consistency: Pretested code reduces bugs and ensures reliability.

• Support: Comes with comprehensive documentation and sample code.

REST API vs. SDK: A side-by-side comparison

Pros

• REST API: Scalable, flexible, platform-independent.

• SDK: Fast, consistent, well-documented.

Cons

• REST API: Requires more coding and error handling.

• SDK: Language-specific, less flexible.

When to use REST API vs. SDK

REST API

• Cross-Platform Integrations: If you’re building a dashboard or system to track e-signature statuses across multiple platforms (e.g., web and mobile), REST APIs are better. They are more flexible, enabling custom requests to interact with various platforms with minimal dependencies.

• Complex Workflows: For managing complex business logic or large-scale integrations, REST APIs give you full control over interactions, which is best for custom workflows.

SDK

• Rapid Development: SDKs are better for integrating eSignature functionality quickly, especially when you’re focused on a specific platform or language. For instance, using the BoldSign Python SDK can simplify the process of adding e-signature features to a Python-based web app.

• Platform-Specific Apps: If you are working with a language or platform-specific application, such as a web app built in Python, an SDK provides prebuilt functions and reduces coding overhead, speeding up the integration.

BoldSign eSignature integration via REST API and SDKs

BoldSign REST API

The BoldSign REST API makes it easy to integrate e-signatures into any app, regardless of language or platform. It works well for developers who need full control over their integration.

Example: Sending an E-Signature Request

Here’s how to use the BoldSign REST API to send a contract.

 import requests

  url = "https://api.boldsign.com/v1/document/send"
  headers = {
      "accept": "application/json",
      "X-API-KEY": "your_api_key"
  }

  payload = {
      "title": "Freelance Agreement",
      "signers": [{
          "name": "Hanky",
          "emailAddress": "hanky@example.com",
          "formFields": [{
              "id": "sig1",
              "fieldType": "Signature",
              "pageNumber": 1,
              "bounds": {"x": 50, "y": 50, "width": 200, "height": 50},
              "isRequired": True
          }]
      }]
  }

  files = [("files", ("contract.pdf", open("contract.pdf", "rb"), "application/pdf"))]

  response = requests.post(url, headers=headers, data=payload, files=files)
  print(f"Document sent! ID: {response.json()['documentId']}")

Result: The freelancer gets an email with a link to sign the contract. You can use webhooks to track its status.

Try It: Generate an API key in BoldSign and test this in under 5 minutes. Check the BoldSign API documentation for more details.

BoldSign SDKs

BoldSign offers SDKs for Python, .NET, Node.js, PHP, and Java to speed up eSignature integration. It is best for developers who want to skip the complexity of raw API calls.

Example: Sending an E-Signature Request with the Python SDK

Here’s how to send a contract using the BoldSign Python SDK.

    from boldsign.configuration import Configuration
    from boldsign.api.document_api import DocumentApi
    from boldsign.model.document_form_field import DocumentFormField
    from boldsign.model.signer import Signer
    from boldsign.model.document import Document

    config = Configuration(api_key="your_api_key")

    with boldsign.ApiClient(config) as client:
        document_api = DocumentApi(client)
        signer = Signer(
            name="Hanky",
            email_address="hanky@example.com",
            form_fields=[DocumentFormField(
                id="sig1", field_type="Signature", page_number=1,
                bounds={"x": 50, "y": 50, "width": 200, "height": 50},
                is_required=True
            )]
        )

        document = Document(
            title="Freelance Agreement",
            signers=[signer],
            files=["contract.pdf"]
        )

        response = document_api.document_send(document)
        print(f"Document sent! ID: {response.document_id}")

Result: Just like with the REST API, the recipient gets a signing link via email, and you’re notified when it’s done.

Try It: Install the SDK with pip install boldsign and test it out. You can refer to the documentation for more details on this.

Quick-decision guide

• Use REST APIs for cross-platform apps, full control, or minimal dependencies.

• Use SDKs for fast, language-specific integration or simpler development.

Conclusion

Choosing between a REST API and an SDK for your eSignature integration depends on your project’s needs and development goals. BoldSign offers both options, making it easy to build seamless, secure, and scalable eSignature workflows.

Ready to try it out? Sign up for a free BoldSign account, explore the developer documentation, and test REST APIs or SDKs today. Have questions? Reach out via the support portal or share your thoughts in the comments section below!

Related blogs

• API Key Vs. OAuth – How to Choose the best Authentication

• Introducing BoldSign Node.js SDK for effortless E-Signature integration

• Introducing the BoldSign Python SDK for Effortless E-Signature Integration

Note: This blog was originally published at boldsign.com