Formatting E.164 Phone Numbers in Genesys Cloud Architect Using Expression Language

StarAdmin · May 22, 2026, 9:00am

Formatting E.164 Phone Numbers in Genesys Cloud Architect Using Expression Language

What You Will Build

One sentence: You will build a Genesys Cloud Architect flow that accepts an E.164 phone number (e.g., +12125551234) and outputs a US-formatted string ((212) 555-1234).
One sentence: This uses the Genesys Cloud Architect Expression Language (CEL-like syntax) within a Flow Action.
One sentence: The tutorial covers the specific string manipulation functions available in Genesys Cloud Architect, as well as how to validate the input via the Genesys Cloud API to ensure data integrity before formatting.

Prerequisites

Access Level: You need “Flow Editor” permissions in Genesys Cloud to create or edit flows.
Knowledge Base: Familiarity with Genesys Cloud Architect drag-and-drop interface and the concept of “Attributes” and “Data Sets”.
API Access (for Validation Step): A Genesys Cloud Organization with API credentials. We will use the Python SDK (genesyscloud) to demonstrate how to validate phone numbers programmatically before they enter the formatting logic.
Dependencies: genesyscloud Python package (version 12.0+).

Authentication Setup

Before writing the Architect expression, it is best practice to validate that the incoming number is actually a valid E.164 number. Genesys Cloud provides a Telephony Management API for this. We will use the Python SDK to authenticate and perform a validation check. This ensures that the Architect expression only processes clean data.

Install the SDK:

pip install genesyscloud

Here is the authentication setup using OAuth2 Client Credentials flow. This is the standard method for server-to-server API calls.

import sys
from purecloudplatformclientv2 import (
    ApiClient,
    Configuration,
    TelephonyManagementApi,
    PhoneNumberValidationRequest
)

# Configuration
CLIENT_ID = "your_client_id"
CLIENT_SECRET = "your_client_secret"
ORG_DOMAIN = "your_domain" # e.g., "mypurecloud.com"

def create_api_client():
    """
    Creates and returns an authenticated API client.
    """
    config = Configuration(
        host=f"https://{ORG_DOMAIN}/api/v2",
        client_id=CLIENT_ID,
        client_secret=CLIENT_SECRET
    )
    
    # The SDK handles token refresh automatically
    api_client = ApiClient(configuration=config)
    return api_client

def validate_phone_number(api_client: ApiClient, phone_number: str) -> bool:
    """
    Validates a phone number using Genesys Cloud Telephony Management API.
    Returns True if valid, False otherwise.
    """
    telephony_api = TelephonyManagementApi(api_client)
    
    try:
        # Construct the validation request
        request_body = PhoneNumberValidationRequest(
            number=phone_number
        )
        
        # Call the API
        # Endpoint: POST /api/v2/telephony/phone/numbers/validation
        response = telephony_api.post_telephony_phone_numbers_validation(
            body=request_body
        )
        
        # Check the validation result
        # The response contains a 'valid' boolean and 'formatted' options
        if response.valid:
            print(f"Number {phone_number} is valid. Formatted: {response.formatted}")
            return True
        else:
            print(f"Number {phone_number} is invalid.")
            return False
            
    except Exception as e:
        print(f"Error validating number: {e}")
        return False

if __name__ == "__main__":
    client = create_api_client()
    # Example: Validate +12125551234
    is_valid = validate_phone_number(client, "+12125551234")

OAuth Scope Required: telephony:phone:read

Implementation

Step 1: Understanding the Architect Expression Syntax

Genesys Cloud Architect uses a specific expression language for transforming data. It does not support arbitrary Python or JavaScript code. Instead, it provides a set of built-in functions for string manipulation, math, and date handling.

To format a phone number, you cannot use a single “format phone” function. You must construct it using substring extraction and concatenation.

Assume the input attribute is {{contact.attributes.phoneNumber}}.
The input format is E.164: +12125551234.

We need to extract:

Area Code: Characters 2, 3, 4 (indices 1, 2, 3 in 0-based indexing, but Genesys uses 1-based indexing for substring).
Prefix: Characters 5, 6, 7.
Line Number: Characters 8, 9, 10, 11.

Critical Note on Indexing:
In Genesys Cloud Architect expressions, the substring function uses 1-based indexing.
substring(string, start, length)

start: The starting position (1 = first character).
length: The number of characters to extract.

For +12125551234:

Index 1: +
Index 2: 1 (Country Code)
Index 3: 2 (Start of Area Code)
Index 6: 2 (End of Area Code)
Index 7: 5 (Start of Prefix)
Index 10: 5 (End of Prefix)
Index 11: 1 (Start of Line Number)
Index 14: 4 (End of Line Number)

Step 2: Constructing the Expression

We will build the expression step-by-step using the concat and substring functions.

Extract Area Code: substring({{contact.attributes.phoneNumber}}, 3, 3)
- Starts at index 3 (the first digit of the area code, skipping +1).
- Length 3.
- Result: 212
Extract Prefix: substring({{contact.attributes.phoneNumber}}, 6, 3)
- Starts at index 6.
- Length 3.
- Result: 555
Extract Line Number: substring({{contact.attributes.phoneNumber}}, 9, 4)
- Starts at index 9.
- Length 4.
- Result: 1234

Concatenate with Formatting:
We need to add parentheses and hyphens.

concat(
    "(",
    substring({{contact.attributes.phoneNumber}}, 3, 3),
    ") ",
    substring({{contact.attributes.phoneNumber}}, 6, 3),
    "-",
    substring({{contact.attributes.phoneNumber}}, 9, 4)
)

Edge Case: Non-US Numbers
The above expression assumes a 10-digit US/Canada number preceded by +1. If the input is a UK number like +442079460123, this expression will break or produce garbage.

To make it robust, you should first check the length or the country code. However, Architect expressions do not support complex if-else logic inline within a single attribute assignment easily without using a “Set Attribute” action with conditions or a “Data Set” lookup.

For this tutorial, we will assume the input is guaranteed to be a US E.164 number (+1...) because the previous Python validation step can filter out non-US numbers if required.

Step 3: Implementing in Architect Flow

Open your Genesys Cloud Organization.
Navigate to Admin > Engagement > Flows.
Create a new Inbound Email or Inbound Voice flow (Voice is more common for phone numbers).
Add a Set Attribute action.
Configure the action:
- Attribute Name: formatted_phone
- Value: Select “Expression”.
- Expression: Paste the code below.

concat(
    "(",
    substring({{contact.attributes.phoneNumber}}, 3, 3),
    ") ",
    substring({{contact.attributes.phoneNumber}}, 6, 3),
    "-",
    substring({{contact.attributes.phoneNumber}}, 9, 4)
)

Save the action.
Add a Log Message action after it to verify the output.
- Message: Formatted Phone: {{contact.attributes.formatted_phone}}

Step 4: Handling Invalid Lengths with Fallback

If the input number is not exactly 12 characters long (e.g., +1 + 10 digits), the substring function may return an empty string or throw an error depending on the platform version. A safer approach is to use the if function available in newer Architect versions.

However, standard if in expressions is limited. A better architectural pattern is to use a Decision node before the Set Attribute node.

Add a Decision node.
Condition: {{contact.attributes.phoneNumber}} matches regex ^\+1\d{10}$
- Note: Genesys Architect supports basic regex matching in decisions.
If True: Proceed to the Set Attribute node defined in Step 3.
If False: Proceed to a “Log Error” or “Set Default” node.

This ensures that the expression only runs on valid data.

Complete Working Example

Below is the complete Python script that validates the number, and the corresponding Architect Expression configuration.

Python Validation Script (Pre-Processing)

import sys
from purecloudplatformclientv2 import (
    ApiClient,
    Configuration,
    TelephonyManagementApi,
    PhoneNumberValidationRequest
)

# Replace with your credentials
CLIENT_ID = "YOUR_CLIENT_ID"
CLIENT_SECRET = "YOUR_CLIENT_SECRET"
ORG_DOMAIN = "YOUR_ORG_DOMAIN"

def get_api_client():
    config = Configuration(
        host=f"https://{ORG_DOMAIN}/api/v2",
        client_id=CLIENT_ID,
        client_secret=CLIENT_SECRET
    )
    return ApiClient(configuration=config)

def validate_and_format_us_number(phone_number: str) -> dict:
    """
    Validates a US phone number and returns a formatted string if valid.
    """
    client = get_api_client()
    telephony_api = TelephonyManagementApi(client)
    
    try:
        request = PhoneNumberValidationRequest(number=phone_number)
        response = telephony_api.post_telephony_phone_numbers_validation(body=request)
        
        if response.valid and response.country_code == "US":
            # Extract the national number (without country code)
            # Note: The API returns the national number in various formats.
            # We will rely on the original input for consistent parsing if API format varies.
            
            # Check if it matches E.164 US format: +1XXXXXXXXXX
            if phone_number.startswith("+1") and len(phone_number) == 12:
                area_code = phone_number[2:5]
                prefix = phone_number[5:8]
                line_num = phone_number[8:12]
                formatted = f"({area_code}) {prefix}-{line_num}"
                return {"valid": True, "formatted": formatted}
            else:
                return {"valid": False, "error": "Not a standard US E.164 format"}
        else:
            return {"valid": False, "error": "Invalid number or not US"}
            
    except Exception as e:
        return {"valid": False, "error": str(e)}

# Test the function
if __name__ == "__main__":
    test_number = "+12125551234"
    result = validate_and_format_us_number(test_number)
    print(result)

Architect Expression Configuration

In the Genesys Cloud Architect UI, inside a Set Attribute action:

Attribute Name:
contact.attributes.formatted_phone

Value Type:
Expression

Expression:

concat(
    "(",
    substring({{contact.attributes.phoneNumber}}, 3, 3),
    ") ",
    substring({{contact.attributes.phoneNumber}}, 6, 3),
    "-",
    substring({{contact.attributes.phoneNumber}}, 9, 4)
)

Pre-Requisite Decision Node:
Ensure you have a Decision node prior to this Set Attribute action with the condition:
{{contact.attributes.phoneNumber}} matches ^\+1\d{10}$

This ensures the expression only executes on valid 12-character US numbers.

Common Errors & Debugging

Error: `Invalid expression` or `Syntax error`

Cause:

Missing commas between arguments in concat.
Using 0-based indexing instead of 1-based indexing.
Using quotes incorrectly (must use double quotes ").

Fix:

Ensure every argument in concat is separated by a comma.
Remember: substring(string, 1, 10) gets the first 10 characters. substring(string, 0, 10) is invalid.

Example of correct syntax:

concat("(", substring({{contact.attributes.phoneNumber}}, 3, 3), ")")

Error: Output is `(21) 25-5512` (Misaligned)

Cause:

The input number does not start with +1. For example, if the input is 2125551234 (10 digits, no country code), the indices are off by 2.
Index 3 in 2125551234 is 2 (the second digit of the area code), not the start.

Fix:

Normalize the input before formatting. Use a Set Attribute to prepend +1 if the number is 10 digits and does not start with +.
Decision Node: If {{contact.attributes.phoneNumber}} length is 10 and does not start with +, set {{contact.attributes.phoneNumber}} to concat("+1", {{contact.attributes.phoneNumber}}).

Error: `Null` or Empty String Output

Cause:

The substring indices exceed the string length. For example, trying to extract 4 characters starting at index 9 from a string that is only 11 characters long.
The input attribute {{contact.attributes.phoneNumber}} is null.

Fix:

Use the Decision Node pattern described in Step 4 to validate length before formatting.
Add a fallback value in the Set Attribute action if possible, or handle the null case in a parallel flow path.

Formatting E.164 Phone Numbers in Genesys Cloud Architect Using Expression Language

Formatting E.164 Phone Numbers in Genesys Cloud Architect Using Expression Language

What You Will Build

Prerequisites

Authentication Setup

Implementation

Step 1: Understanding the Architect Expression Syntax

Step 2: Constructing the Expression

Step 3: Implementing in Architect Flow

Step 4: Handling Invalid Lengths with Fallback

Complete Working Example

Python Validation Script (Pre-Processing)

Architect Expression Configuration

Common Errors & Debugging

Error: Invalid expression or Syntax error

Error: Output is (21) 25-5512 (Misaligned)

Error: Null or Empty String Output

Official References

Error: `Invalid expression` or `Syntax error`

Error: Output is `(21) 25-5512` (Misaligned)

Error: `Null` or Empty String Output