What do you want to achieve?
│
├─► CRUD operations on documents
│   └─► REST API: /api/resource/{doctype}
│
├─► Call custom business logic
│   └─► RPC API: /api/method/{path}
│
├─► Notify external systems on events
│   └─► Configure Webhooks
│
└─► Client-side server calls (JavaScript)
    └─► frappe.call() or frappe.xcall()

# Token Auth (RECOMMENDED for integrations)
headers = {
    'Authorization': 'token api_key:api_secret',
    'Accept': 'application/json',
    'Content-Type': 'application/json'
}

# Bearer Token (OAuth2)
headers = {'Authorization': 'Bearer {access_token}'}

# Basic filters
filters = [["status", "=", "Open"]]
filters = [["amount", ">", 1000]]
filters = [["status", "in", ["Open", "Pending"]]]
filters = [["date", "between", ["2024-01-01", "2024-12-31"]]]
filters = [["reference", "is", "set"]]  # NOT NULL

# Server-side: mark with decorator
@frappe.whitelist()
def my_function(param1, param2):
    return {"result": "value"}

# API call
POST /api/method/my_app.api.my_function
{"param1": "value1", "param2": "value2"}

// Async/await pattern (RECOMMENDED)
const result = await frappe.xcall('my_app.api.my_function', {
    param1: 'value'
});

// Promise pattern
frappe.call({
    method: 'my_app.api.my_function',
    args: {param1: 'value'},
    freeze: true,
    freeze_message: __('Processing...')
}).then(r => console.log(r.message));

{"data": {...}}

{"message": "return_value"}

{
    "exc_type": "ValidationError",
    "_server_messages": "[{\"message\": \"Error details\"}]"
}