Learn how to integrate your business software using APIs. A practical guide covering REST APIs, webhooks, authentication, and common integrations for accounting, CRM, inventory, and more.
Your business uses multiple software tools. Your CRM doesn't talk to your accounting software. Your e-commerce platform doesn't sync with your inventory system. Your email marketing tool doesn't know about your sales data.
APIs are how you fix this.
This guide explains what APIs are, how they work, and how to use them to connect your business software—even if you're not a developer.
API stands for Application Programming Interface. It's a way for software applications to talk to each other.
Think of an API like a waiter in a restaurant:
You don't walk into the kitchen. You tell the waiter what you want, and they handle the communication.
When you:
The app is making API calls to:
You don't see any of this—it just works.
Without APIs, your data is trapped:
┌─────────────┐ ┌─────────────┐ ┌─────────────┐
│ CRM │ │ Accounting │ │ Email │
│ │ │ │ │ │
│ Customer │ │ Invoices │ │ Subscribers │
│ List │ │ │ │ │
└─────────────┘ └─────────────┘ └─────────────┘
↓ ↓ ↓
MANUAL MANUAL MANUAL
EXPORT EXPORT EXPORT
↓ ↓ ↓
Excel Excel Excel
With APIs, data flows automatically:
┌─────────────┐ ┌─────────────┐ ┌─────────────┐
│ CRM │◄───►│ Accounting │◄───►│ Email │
│ │ │ │ │ │
│ Customer │ │ Invoices │ │ Subscribers │
│ List │ │ │ │ │
└─────────────┘ └─────────────┘ └─────────────┘
↑ ↑ ↑
└───────────────┼───────────────────┘
│
AUTOMATIC VIA APIs
| Manual Process | With API Integration |
|---|---|
| Hours of data entry | Instant synchronization |
| Human errors | Accurate every time |
| Outdated information | Real-time data |
| One-way data flow | Bi-directional sync |
| Delayed decisions | Immediate visibility |
REST (Representational State Transfer) is the standard for web APIs.
How it works:
Example: Get a customer from HubSpot
GET https://api.hubapi.com/contacts/v1/contact/email/john@example.com
Authorization: Bearer your-api-key
Response:
{
"vid": 12345,
"properties": {
"firstname": "John",
"lastname": "Smith",
"email": "john@example.com",
"company": "Acme Corp"
}
}
Webhooks push data to you when something happens, rather than you asking for it.
Without webhooks: You check every minute: "Any new orders?" With webhooks: The system tells you: "New order just came in!"
Example: Stripe webhook for payment
POST https://your-app.com/webhooks/stripe
{
"type": "payment_intent.succeeded",
"data": {
"object": {
"amount": 9900,
"currency": "usd",
"customer": "cus_ABC123"
}
}
}
GraphQL lets you request exactly the data you need.
REST: Get entire customer object, even if you only need the email GraphQL: Get only the email
Example:
query {
customer(id: "12345") {
email
recentOrders(limit: 5) {
total
date
}
}
}APIs need to know who's making requests. Common methods:
The simplest method. You get a key, include it in requests.
GET https://api.example.com/data
X-API-Key: your-secret-key-here
Security note: Treat API keys like passwords. Never share them publicly.
For applications that access user accounts (like Google, Salesforce).
The flow:
More secure, but more complex to implement.
Common for modern APIs. Include a token in the Authorization header.
GET https://api.example.com/data
Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...
HubSpot, Salesforce, Pipedrive, Zoho CRM
Common use cases:
Example: Create a HubSpot contact from a form
// When form is submitted
const response = await fetch('https://api.hubapi.com/contacts/v1/contact', {
method: 'POST',
headers: {
'Authorization': `Bearer ${HUBSPOT_API_KEY}`,
'Content-Type': 'application/json'
},
body: JSON.stringify({
properties: [
{ property: 'email', value: formData.email },
{ property: 'firstname', value: formData.firstName },
{ property: 'company', value: formData.company }
]
})
});Xero, QuickBooks, FreshBooks
Common use cases:
Example: Create a Xero invoice
const invoice = {
Type: 'ACCREC',
Contact: { ContactID: customerId },
Date: new Date().toISOString(),
DueDate: dueDate,
LineItems: [
{
Description: 'Consulting Services',
Quantity: 10,
UnitAmount: 150.00,
AccountCode: '200'
}
]
};
await xeroClient.invoices.create(invoice);Shopify, WooCommerce, BigCommerce
Common use cases:
Mailchimp, ActiveCampaign, ConvertKit
Common use cases:
Stripe, Square, PayPal
Common use cases:
Let's walk through connecting a contact form to your CRM.
You have a contact form on your website. When someone submits it, you want to:
Using n8n or similar automation tool:
Your webhook receives:
{
"name": "Jane Smith",
"email": "jane@company.com",
"company": "Company Inc",
"message": "I'm interested in your services"
}Add a HubSpot node:
Add a Slack node:
"New lead: [name] from [company]"Add a Mailchimp node:
[email from form]APIs fail. Networks go down. Rate limits get hit. Plan for it.
| Error Code | Meaning | What to Do |
|---|---|---|
| 400 | Bad request (your data is wrong) | Fix the data format |
| 401 | Unauthorized | Check your API key |
| 403 | Forbidden | Check permissions |
| 404 | Not found | Check the endpoint URL |
| 429 | Rate limited | Slow down requests |
| 500 | Server error | Retry after a delay |
For temporary failures, retry with exponential backoff:
Attempt 1: Immediate
Attempt 2: Wait 1 second
Attempt 3: Wait 2 seconds
Attempt 4: Wait 4 seconds
Attempt 5: Give up, alert team
Always know when integrations fail:
❌ Never:
✅ Always:
All API requests should use HTTPS (not HTTP).
For webhooks, verify the sender:
Follow least privilege:
For non-developers:
For understanding and debugging:
When working with an API:
Data flows in one direction only.
Example: New Shopify orders → Accounting system
Pros: Simple to implement Cons: No feedback loop
Data flows both directions, staying in sync.
Example: CRM contacts ↔ Email marketing contacts
Pros: Always synchronized Cons: Conflict resolution needed
Actions trigger on specific events.
Example: Payment received → Send receipt → Update CRM → Notify team
Pros: Real-time, efficient Cons: Requires webhook support
Process data on a schedule.
Example: Every night, sync all orders to accounting
Pros: Reliable, handles large volumes Cons: Not real-time
While many integrations are simple enough to DIY, some scenarios benefit from professional help:
We specialize in API integrations for SMBs:
Book a free consultation to discuss your integration needs.
APIs are the key to unlocking the full potential of your business software. Instead of data trapped in silos and hours spent on manual entry, you can have:
Start with one integration. Master the basics. Then expand.
The businesses that connect their systems effectively will outpace those that don't. It's not just about efficiency—it's about having the right data, at the right time, to make better decisions.
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