How to Connect Any Two Tools With a Custom API Integration

Most automation platforms advertise thousands of native integrations — but what happens when the tool your business uses isn't on the list? The answer is a custom HTTP/REST API integration using Make.com's HTTP module or n8n's HTTP Request node. This guide shows you exactly how.

What You Need to Get Started

The API documentation for the tool you want to connect
An API key, OAuth token, or other credential for authentication
Make.com or n8n as your automation platform

Step 1: Understand the API Documentation

Every REST API has endpoints (URLs), methods (GET, POST, PUT, DELETE), and required parameters. Find the documentation and identify the specific endpoint you need. For example, to create a contact in a CRM, you might call POST /api/v1/contacts.

Step 2: Handle Authentication

Most APIs use one of these three patterns:

API Key Header: Add Authorization: Bearer YOUR_API_KEY to request headers
Basic Auth: Base64-encode username:password and pass as Authorization header
OAuth 2.0: Exchange credentials for a bearer token, then use that token in all requests

// Make.com HTTP Module Configuration: Method: POST URL: https://api.yourtool.com/v1/contacts Headers: Authorization: Bearer {{YOUR_API_KEY}} Content-Type: application/json Body (JSON): { "email": "{{1.email}}", "name": "{{1.name}}", "source": "Website Form" }

Step 3: Parse the Response

The API returns a JSON response. In Make.com, the HTTP module automatically parses this so you can map response data into subsequent modules. If the response contains an ID for the newly created record, save it — you'll need it for updates and lookups later.

Step 4: Handle Errors Properly

APIs return error codes. The most common:

401: Authentication failed — check your API key
404: Resource not found — verify the endpoint URL
422: Validation error — your request body has missing/invalid fields
429: Rate limit exceeded — add a delay between requests

"The HTTP module in Make.com or n8n unlocks connection to literally any tool with an API — which means your automation stack is never limited by a missing native integration."

Real-World Example: Connecting Calendly to Notion

Calendly's free plan doesn't support webhooks — but it does have a REST API. Using Make.com's HTTP module, I poll the Calendly API every 15 minutes for new scheduled events and write them to a Notion database, creating a full CRM entry for every booking without paying for Calendly's premium plan.