Sales engagement

Check phone numbers, phone complaints and carriers in Reply.io

Subscribe a Reply.io webhook to call events and validate the number behind each call, using the contact custom fields the event carries.

Why the data matters in Reply.io

Reply.io runs email, calls and other steps in one sequence, so a contact whose phone is formatted loosely or sits in the wrong country can make the call step fail while the rest of the sequence keeps going. The call outcome then gets logged against a contact that was never reachable by that number to begin with.

What LookValid checks

LookValid checks for Reply.io
Product	What it does here	Credits
Phone Numbering-Plan Validation	Returns E.164 and display formats, the country and the number type the numbering plan assigns for a contact number. It does not say whether the number is active.	1 credit per valid number
Phone Spam Check	Shows consumer complaint counts for a number as reports nobody has checked, which tells a rep a number has a history before the call step runs.	1 credit per number with complaints on record
Carrier Lookup (original carrier)	For US numbers, shows the carrier first assigned the number block with its state and rate center. Porting is not reflected.	1 credit per lookup (numbers outside the covered numbering plan areas are free)
Email Domain Check	Checks the contact email domain for mail servers and throwaway providers when an email bounces, without contacting the mail server.	1 credit per address checked

Connect it in four steps

Open a LookValid account and create an API key.
Set the key as the LOOKVALID_API_KEY environment variable of the webhook handler, and enable includeProspectCustomFields on the Reply.io subscription so the contact custom fields arrive in contact_custom_fields.
Pass the phone from the event contact to the function: it posts to the phone endpoint, returns None when nothing was found and raises with the error code and fix if the API refuses.
Write the three values back to the contact as custom fields through the Reply.io v3 API, using your Reply.io key as a bearer token, so later sequence steps can read them.

the handler for a Reply.io webhook subscription that receives contact call events The call is POST https://YOUR_API_HOST/v1/phone and costs 1 credit per valid number.

validate_reply_contact_phone.py

1import json
2import os
3import urllib.error
4import urllib.request
5
6API_URL = "https://YOUR_API_HOST/v1/phone"
7
8
9def validate_reply_contact_phone(value):
10    request = urllib.request.Request(
11        API_URL,
12        data=json.dumps({
13            "phone": value,
14        }).encode(),
15        headers={
16            "Authorization": "Bearer " + os.environ["LOOKVALID_API_KEY"],
17            "Content-Type": "application/json",
18        },
19        method="POST",
20    )
21    try:
22        with urllib.request.urlopen(request, timeout=30) as response:
23            result = json.load(response)
24    except urllib.error.HTTPError as error:
25        failure = json.load(error)["error"]
26        raise RuntimeError(failure["code"] + ": " + failure["fix"])
27    if not result["found"]:
28        return None
29    return {
30        "phone_e164": result.get("data", {}).get("e164"),
31        "phone_type": result.get("data", {}).get("number_type"),
32        "phone_country": result.get("data", {}).get("country"),
33    }

Where each response field goes in Reply.io
Response field	Goes into
data.e164	phone_e164
data.number_type	phone_type
data.country	phone_country

The recipe returns nothing when the lookup finds nothing, which costs no credits for this product, and stops with the error code and fix on a failed request.

Without code

The webhook subscription delivers each event to a URL of your choice, so an automation platform with a generic HTTP request step can be the receiver without a dedicated app. After the catch trigger, send the contact phone to the phone endpoint with your key in a bearer header, then add an HTTP step that updates the contact through the Reply.io API.

REST and MCPOne shared credit balance

Questions

Does every event cost credits?

Only the lookups your handler makes. Each one draws credits from your LookValid balance, and the pricing page lists the amount for the phone check.

What will the check not tell me about a contact number?

Whether the line is live, who the carrier is now, or who owns it. It reads the numbering plan only.

Where does the LookValid key sit in a Reply.io integration?

In the handler environment as LOOKVALID_API_KEY. The Reply.io key that calls its own API is a separate bearer token, kept in another variable.

Sources

Reply.io API reference: introduction https://docs.reply.io/api-reference/introduction, read 2026-10-18
Reply.io docs: webhook event payloads https://docs.reply.io/webhook-event-payloads.md, read 2026-10-18
LookValid API reference: Phone Numbering-Plan Validation https://lookvalid.com/docs/api/phone, read 2026-10-18

LookValid is run by Meralume Labs. It is not connected to, endorsed by or a partner of any company or product named on this page, and every product name belongs to its owner.

LookValid bills every lookup in credits from one shared balance, so the same key works for each check above.

See Phone Numbering-Plan Validation