Check recipient capabilities

Once you have a Verified Calls agent, you can register calls. However, there's no need to register a call or update a call's state if the call recipient doesn't support Verified Calls. Before you register a call, you can check the recipient device's capabilities to see if it supports Verified Calls.


Before you can check if a recipient can receive Verified Calls, you need to gather some information:

  • Path to your GCP project's service account key on your development machine
  • The recipient's phone number, in E.164 format (for example, "+12223334444")

Additionally, you need the gcloud command line tool installed on your development machine.

Perform a capability check

To check a recipient's capabilities, run the following commands. Replace variables with values you identified in Prerequisites.

  1. Prepare your credentials.


ACCESS_TOKEN="$(gcloud auth application-default print-access-token)"


import json
import os
import time
import jwt
import requests

# Read the path for your service account from environment variables (make sure to set the path)
service_account_path = os.environ.get('PATH_TO_SERVICE_ACCOUNT_KEY')
current_time = round(time.time())

# Open the json service account key
with open(service_account_path) as f:
    service_key = json.load(f)

# Prepare the payload and headers for OAuth
payload = {
    'iss': service_key['client_email'],
    'scope': '',
    'aud': '',
    'exp': current_time + 3600,
    'iat': current_time}
additional_headers = {'kid': service_key['private_key']}

# Encode the jwt
signed_jwt = jwt.encode(payload, service_key['private_key'],
                            headers=additional_headers, algorithm='RS256')

# Prepare the data and make the OAUTH request
data = {
    'grant_type': 'urn:ietf:params:oauth:grant-type:jwt-bearer',
    'assertion': signed_jwt
response ='', data=data)

# Save the access token
token = json.loads(response.text)['access_token']

For full example see our client samples


For more examples see our client samples

  1. Check the recipient's capabilities.


curl -X POST "" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer $ACCESS_TOKEN" \
  -d "{


headers = {
        'Content-Type': 'application/json',
        'Authorization': 'Bearer {}'.format(token),
data = {'deviceNumber': '+16400000000'}

response ='',

For full example see our client samples


For more examples see our client samples

The response includes a value of whether or not the recipient supports Verified Calls. If the response comes back UNREACHABLE for your test device, make sure you've followed the steps to become a beta tester. Otherwise, the number you're calling may be on an incompatible device, or has opted out of the feature.

Next steps

Now that you can check if a device supports Verified Calls, you can register calls.