DEV Community

Sebastian Snow
Sebastian Snow

Posted on

I Built an API That Parses Any Contract into Structured JSON

#webdev #programming #ai #productivity

I Built an API That Parses Any Contract into Structured JSON

Every company deals with contracts. NDAs, employment agreements, leases, SaaS terms — they all contain critical data buried in unstructured text. Extracting that data manually is slow, expensive, and error-prone.

So I built Clausify — an API that takes any contract document and returns clean, structured JSON with all the key fields extracted.

What It Does

Upload a contract (PDF, Word, scanned image, or text file), and Clausify returns structured data like this:

{
  "parties": [
    {
      "name": "Acme Corporation",
      "address": "123 Business Ave, New York, NY",
      "representative": "John Smith, CEO"
    },
    {
      "name": "Beta Technologies LLC",
      "address": "456 Tech Road, San Francisco, CA",
      "representative": "Jane Doe, CTO"
    }
  ],
  "effective_date": "2024-01-15",
  "duration": "3 years",
  "obligations_of_receiving_party": "Shall not disclose any Confidential Information to third parties without prior written consent.",
  "governing_law": "State of New York"
}
Enter fullscreen mode Exit fullscreen mode

One API call. No ML pipeline to set up. No training data needed.

How to Use It

1. Get Your API Key

Sign up on RapidAPI and subscribe to the free plan (20 requests/month).

2. Parse a Contract

cURL:

curl -X POST "https://clausify.p.rapidapi.com/v1/extractions" \
  -H "X-RapidAPI-Key: YOUR_API_KEY" \
  -H "X-RapidAPI-Host: clausify.p.rapidapi.com" \
  -F "file=@contract.pdf" \
  -F "contract_type=nda"
Enter fullscreen mode Exit fullscreen mode

Python:

import requests

url = "https://clausify.p.rapidapi.com/v1/extractions"
headers = {
    "X-RapidAPI-Key": "YOUR_API_KEY",
    "X-RapidAPI-Host": "clausify.p.rapidapi.com"
}

with open("contract.pdf", "rb") as f:
    response = requests.post(
        url,
        headers=headers,
        files={"file": f},
        data={"contract_type": "nda"}
    )

data = response.json()
print(data["result"])
Enter fullscreen mode Exit fullscreen mode

JavaScript:

const form = new FormData();
form.append("file", fs.createReadStream("contract.pdf"));
form.append("contract_type", "nda");

const response = await fetch(
  "https://clausify.p.rapidapi.com/v1/extractions",
  {
    method: "POST",
    headers: {
      "X-RapidAPI-Key": "YOUR_API_KEY",
      "X-RapidAPI-Host": "clausify.p.rapidapi.com",
    },
    body: form,
  }
);

const data = await response.json();
console.log(data.result);
Enter fullscreen mode Exit fullscreen mode

3. Choose Your Contract Type

Clausify has 6 built-in templates optimized for different contract types:

Type What It Extracts
general Parties, dates, obligations, price, terms
nda Confidential info definition, duration, exclusions
employment Salary, benefits, probation, non-compete
lease Rent, deposit, maintenance, renewal terms
saas SLA, data handling, liability, auto-renewal
procurement Goods, quantity, delivery, warranty, penalties

Or pass custom fields to extract exactly what you need:

-F 'fields=["vendor_name", "payment_deadline", "penalty_clause"]'
Enter fullscreen mode Exit fullscreen mode

Use Cases

Legal Tech Platforms — Auto-populate case management systems with contract data.

HR Software — Parse employment contracts to extract salary, benefits, and start dates.

Real Estate Tools — Extract lease terms, rent amounts, and renewal dates from rental agreements.

Procurement Systems — Pull vendor info, pricing, and delivery dates from purchase orders.

Due Diligence — Batch-process hundreds of contracts during M&A and extract key terms.

How I Built It

The tech stack is straightforward:

  • FastAPI for the API framework
  • GPT for intelligent extraction (not regex — it understands context)
  • PyMuPDF for PDF text extraction
  • python-docx for Word documents
  • GPT Vision for scanned documents (built-in OCR)
  • Railway for deployment
  • RapidAPI for distribution and billing

The core logic is simple: parse the document into text, send it to GPT with a contract-type-specific prompt, and return structured JSON. The magic is in the prompt engineering — each contract type has an optimized extraction template.

Pricing

Plan Price Requests
Basic Free 20/month
Pro $9.99/mo 200/month
Ultra $29.99/mo 800/month
Mega $69.99/mo 3000/month

Try It

The free tier gives you 20 requests to test with your own contracts:

Try Clausify on RapidAPI →

I'd love to hear your feedback — what contract types or features would be most useful for your workflow? Drop a comment below.

Top comments (0)