Invocable Functions

Invocable functions create custom HTTP endpoints that execute your code on demand. Use them for custom APIs, webhook handlers, and complex operations.

How It Works

1. Define a unique endpoint path (e.g., calculate-shipping)
2. Configure which HTTP methods are allowed (GET, POST, PUT, DELETE)
3. Set role-based access control per method
4. Write JavaScript code to handle requests
5. Call the endpoint via HTTP

URL Structure

https://<region>.restapi.com/<api-name>/_invoke/<function-name>

Example:

https://eu.restapi.com/my-api/_invoke/calculate-shipping

Configuration

Basic Settings

Setting	Description
Name	Unique identifier for the function (used in URL)
Description	Optional documentation
Enabled	Toggle to enable/disable

HTTP Methods

Configure which methods the endpoint accepts:

Method	Typical Use
GET	Retrieve data, calculations
POST	Create resources, complex operations
PUT	Replace resources
DELETE	Remove resources

Access Control

Unlike trigger and timer functions, invocable functions have role-based access control per HTTP method:

Role	Description
Anonymous user	No authentication required
Authenticated user	Any logged-in user
Custom roles	Your defined roles

Configure different permissions for each method. For example:

• GET → Anonymous (public)
• POST → Authenticated users only
• DELETE → Manager role only

Execution Context

What Your Code Receives

Object	Description
req.bodyJson	Parsed JSON request body
req.body	Raw request body string
req.method	HTTP method (GET, POST, PUT, DELETE)
req.headers	Request headers (filtered for security)
req.query	Query parameters
me	Authenticated user information (if any)
api	API information
secrets	Configured secrets

Returning Responses

Set the res object to return data:

// Return JSON response
res = {
  status: 200,
  bodyJson: {
    success: true,
    result: calculatedValue
  }
};

// Or just set bodyJson (status defaults to 200)
res = {
  bodyJson: { message: 'Done' }
};

Use Cases

Custom Calculations

Perform calculations that require server-side logic:

const { weight, destination, method } = req.bodyJson;

let baseCost = weight * 0.5;

if (destination === 'international') {
  baseCost *= 2.5;
}

if (method === 'express') {
  baseCost *= 1.5;
}

res = {
  bodyJson: {
    shippingCost: Math.round(baseCost * 100) / 100,
    estimatedDays: method === 'express' ? 2 : 7
  }
};

Webhook Handlers

Receive webhooks from external services:

// Handle Stripe webhook
const event = req.bodyJson;

switch (event.type) {
  case 'payment_intent.succeeded':
    const paymentIntent = event.data.object;

    // Update order status using built-in method
    await patch(`orders/${paymentIntent.metadata.orderId}`, {
      paymentStatus: 'paid',
      stripePaymentId: paymentIntent.id
    });
    break;

  case 'payment_intent.payment_failed':
    // Handle failure
    break;
}

res = { bodyJson: { received: true } };

Aggregation Endpoints

Create endpoints that aggregate data:

// Dashboard statistics - use built-in methods
const [ordersRes, customersRes, productsRes] = await Promise.all([
  get('orders?count=true'),
  get('customers?count=true'),
  get('products?count=true')
]);

res = {
  bodyJson: {
    totalOrders: ordersRes.meta?.count || 0,
    totalCustomers: customersRes.meta?.count || 0,
    totalProducts: productsRes.meta?.count || 0,
    recentOrders: ordersRes.data.slice(0, 5)
  }
};

Multi-Step Operations

Orchestrate complex operations:

// Create order with inventory check
const { customerId, items } = req.bodyJson;

// Check inventory using built-in method
for (const item of items) {
  const productRes = await get(`products/${item.productId}`);
  const product = productRes.data[0];

  if (product.stockLevel < item.quantity) {
    res = {
      status: 400,
      bodyJson: {
        error: `Insufficient stock for ${product.name}`,
        available: product.stockLevel
      }
    };
    return;
  }
}

// Create order
const orderRes = await post('orders', {
  customerId,
  items,
  status: 'pending',
  total: items.reduce((sum, i) => sum + i.price * i.quantity, 0)
});

const orderId = orderRes.data[0];

// Reserve inventory
for (const item of items) {
  const productRes = await get(`products/${item.productId}`);
  const product = productRes.data[0];

  await patch(`products/${item.productId}`, {
    stockLevel: product.stockLevel - item.quantity
  });
}

res = { bodyJson: { orderId, status: 'created' } };

Validation with Errors

Use validationErrors for user-facing validation:

const { email, name, age } = req.bodyJson;

if (!email) {
  validationErrors.push('Email is required');
}

if (!name || name.length < 2) {
  validationErrors.push('Name must be at least 2 characters');
}

if (age && age < 18) {
  validationErrors.push('Must be 18 or older');
}

// If validationErrors has items, returns 400 automatically
if (validationErrors.length > 0) {
  return; // Stop execution
}

// Proceed with valid data
const userRes = await post('users', { email, name, age });

res = { bodyJson: { userId: userRes.data[0], created: true } };

External API Integration

Call external APIs (requires paid tier):

// Verify address with external service
const { address } = req.bodyJson;

const verification = await fetch('https://api.addressvalidator.com/verify', {
  method: 'POST',
  headers: {
    'Authorization': `Bearer ${secrets.ADDRESS_API_KEY}`,
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({ address })
});

const result = await verification.json();

res = {
  bodyJson: {
    valid: result.valid,
    standardized: result.standardizedAddress
  }
};

Calling Invocable Functions

From JavaScript

const response = await fetch('https://eu.restapi.com/my-api/_invoke/calculate-shipping', {
  method: 'POST',
  headers: {
    'Authorization': 'Bearer <token>',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    weight: 2.5,
    destination: 'domestic',
    method: 'standard'
  })
});

const result = await response.json();
console.log(result.shippingCost);

From cURL

curl -X POST https://eu.restapi.com/my-api/_invoke/calculate-shipping \
  -H "Authorization: Bearer <token>" \
  -H "Content-Type: application/json" \
  -d '{"weight": 2.5, "destination": "domestic", "method": "standard"}'

Best Practices

• Use meaningful function names — calculate-shipping is better than func1
• Validate input — Check req.bodyJson fields and use validationErrors
• Use built-in methods — get(), post(), patch() for internal API calls
• Use fetch only for external APIs — External calls require paid tier
• Set appropriate access control — Don't expose sensitive operations publicly
• Return consistent responses — Use a standard response structure