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Overview

1. Watches HubSpot for deals moving into a specific stage (e.g. “Demo Done”)
2. Filters deals to only those with a captured ucc referral code
3. Authenticates with the Cello API to obtain an access token
4. Sends a signup event to Cello using the POST /events endpoint

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Prerequisites

• A HubSpot account with deals flowing through your sales pipeline
• A Zapier account (Starter plan or above — Code by Zapier steps require a paid plan)
• A Cello account with API credentials (accessKeyId and secretAccessKey) — generate these in the Cello Portal
• A ucc property on your HubSpot deal or company object, populated when the referral lands. Follow the HubSpot Forms attribution guide to set this up.
• Cello JS Referral Component integrated in your product so referrers can share referral links

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The completed Zap

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Step 1: Trigger on HubSpot deal stage change

1. In Zapier, create a new Zap and choose HubSpot as the trigger app.
2. Pick the event “Deal in stage” (or “Deal Property Changed” depending on your HubSpot plan).
3. Select your Deal Pipeline and the Deal Stage that should trigger the event (e.g. Demo Done/Purchase Consideration).
4. Under Additional properties to retrieve, add the ucc property so it’s available in later steps.

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Step 2: Filter deals without a ucc

1. Choose Filter by Zapier.
2. Set the rule to: 1. Deal information: ucc Exists.

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Step 3: Create a Cello access token

1. Choose Code by Zapier → Run Python.
2. Leave Input Data empty (credentials are hardcoded in this step).
3. Paste the snippet below and replace <accessKeyId> and <secretAccessKey> with your Cello API credentials.

import json
import urllib.request

ACCESS_KEY_ID = "<accessKeyId>"
SECRET_ACCESS_KEY = "<secretAccessKey>"

body = {
    "accessKeyId": ACCESS_KEY_ID,
    "secretAccessKey": SECRET_ACCESS_KEY
}

req = urllib.request.Request(
    url="https://api.cello.so/token",
    data=json.dumps(body).encode("utf-8"),
    method="POST",
    headers={"Content-Type": "application/json"}
)

try:
    with urllib.request.urlopen(req, timeout=10) as resp:
        data = json.loads(resp.read().decode("utf-8"))
    output = {
        "access_token": data.get("accessToken"),
        "expires_in": data.get("expiresIn"),
        "status": resp.status
    }
except urllib.error.HTTPError as e:
    output = {
        "access_token": "",
        "status": e.code,
        "error": e.read().decode("utf-8")
    }

​

Step 4: Send the signup event to Cello

1. Choose Code by Zapier → Run Python.
2. Map the following Input Data fields from the previous steps:

   Input Data key	Map from
   access_token	Step 3 → Access Token
   ucc	Step 1 → Deal information: ucc
   user_id	Step 1 → Deal information: Record ID (or your own product user ID property)
   email	Step 1 → Deal information: email_of_demo_request (or contact email)
   name	Step 1 → Deal information: Deal Name (or contact name)
   org_id	Step 1 → company / organization ID (optional)

3. Paste the snippet below:

import json
import urllib.request
from datetime import datetime, timezone

access_token = input_data.get("access_token", "")
ucc = input_data.get("ucc", "")
user_id = input_data.get("user_id", "")
email = input_data.get("email", "")
name = input_data.get("name", "")
org_id = input_data.get("org_id", "")

timestamp = datetime.now(timezone.utc).strftime("%Y-%m-%d %H:%M:%S")

body = {
    "eventName": "ReferralUpdated",
    "payload": {
        "ucc": ucc,
        "newUserId": user_id
    },
    "context": {
        "newUser": {
            "id": user_id,
            "email": email,
            "name": name,
            "organizationId": org_id
        },
        "event": {
            "trigger": "demo-call-attended",
            "timestamp": timestamp
        }
    }
}

req = urllib.request.Request(
    url="https://api.cello.so/events",
    data=json.dumps(body).encode("utf-8"),
    method="POST",
    headers={
        "Content-Type": "application/json",
        "Authorization": f"Bearer {access_token}"
    }
)

try:
    with urllib.request.urlopen(req, timeout=10) as resp:
        response_body = resp.read().decode("utf-8")
        output = {"status": resp.status, "response": response_body}
except urllib.error.HTTPError as e:
    output = {"status": e.code, "response": e.read().decode("utf-8")}

​

Step 5: Verify and publish

1. Publish your Zap.
2. Move a test deal into the trigger stage in HubSpot.
3. Wait up to 15 minutes for Zapier to pick up the change.
4. Open the Event Feed in the Cello Portal and confirm the event was received with the correct ucc, newUserId, and trigger.
5. Check Integration Status — Signups should now show as Connected.

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Variations

• Different trigger stages. Duplicate the Zap and change the HubSpot deal stage + event.trigger value to track multiple milestones (e.g. one Zap for demo-call-attended, another for qualified-lead).
• Reward at the organization level. Set newUserId to the HubSpot company ID instead of the deal/contact ID, and populate newUser.organizationId accordingly. See Tracking Signups for the organization-level attribution model.
• Use the Zapier HTTP action instead of Code steps. If you prefer not to write Python, both API calls can be done with Webhooks by Zapier → POST. The body and headers are the same as in the snippets above.