How to Integrate a Third-Party Logistics API for Shipping and Tracking in Flu...

Create a ShipEngine account at shipengine.com. From the API Keys section, copy your API key. In your Firebase functions directory, set the key in environment variables: firebase functions:config:set shipengine.key='SE-YOUR_KEY'. In the ShipEngine dashboard, connect carrier accounts. ShipEngine provides a built-in test USPS account for development. To add FedEx or UPS, you need existing carrier accounts with those providers — connect them in ShipEngine's Carriers section. Each connected carrier appears automatically in rate quotes. You do not need separate API accounts for each carrier once they are connected to ShipEngine.

Create a Cloud Function named validateAddress. It accepts to_name, to_company, address_line1, address_line2, city_locality, state_province, postal_code, country_code as query or body parameters. Call ShipEngine's address validation endpoint: POST https://api.shipengine.com/v1/addresses/validate with header API-Key. ShipEngine returns status: verified, unverified, or error, plus any corrections to the address fields (normalized street name, city, state). Return the validated address to FlutterFlow. Show any corrections to the user for confirmation: 'We normalized your address to: 123 Main St Apt 4 → 123 MAIN ST STE 4. Is this correct?' This prevents shipping label creation with invalid addresses.

Create a Cloud Function named getRates. It accepts shipFrom and shipTo address objects, weight (in ounces or grams), dimensions (length, width, height), and a list of carrier IDs. Call ShipEngine POST /v1/rates with the shipment object. ShipEngine returns an array of rate objects across all connected carriers and service levels, each with: carrier_id, carrier_friendly_name, service_code, service_type, shipping_amount.amount (price), delivery_days, estimated_delivery_date, trackable. Filter out rates with error_messages. Sort by shipping_amount ascending. Return the top 5-10 rates. In FlutterFlow, create an API Group pointing to this Cloud Function and display results in a ListView — each rate row shows carrier logo icon, service name, delivery days, and price.

1const functions = require('firebase-functions');
2const axios = require('axios');
3
4const API_KEY = functions.config().shipengine.key;
5
6exports.getRates = functions.https.onRequest(async (req, res) => {
7  res.set('Access-Control-Allow-Origin', '*');
8  if (req.method === 'OPTIONS') return res.status(204).send('');
9
10  const { shipFrom, shipTo, weight, dimensions } = req.body;
11  if (!shipFrom || !shipTo || !weight) {
12    return res.status(400).json({ error: 'shipFrom, shipTo, and weight required' });
13  }
14
15  try {
16    const { data } = await axios.post(
17      'https://api.shipengine.com/v1/rates',
18      {
19        rate_options: { carrier_ids: [], calculate_tax_amount: false },
20        shipment: {
21          ship_from: shipFrom,
22          ship_to: shipTo,
23          packages: [{ weight: { value: weight, unit: 'ounce' }, dimensions }],
24        },
25      },
26      { headers: { 'API-Key': API_KEY, 'Content-Type': 'application/json' } }
27    );
28
29    const rates = (data.rate_response?.rates || [])
30      .filter((r) => !r.error_messages?.length)
31      .sort((a, b) => a.shipping_amount.amount - b.shipping_amount.amount)
32      .slice(0, 10)
33      .map((r) => ({
34        rateId: r.rate_id,
35        carrier: r.carrier_friendly_name,
36        service: r.service_type,
37        price: r.shipping_amount.amount,
38        currency: r.shipping_amount.currency,
39        deliveryDays: r.delivery_days,
40        estimatedDelivery: r.estimated_delivery_date,
41      }));
42
43    res.json({ rates });
44  } catch (err) {
45    res.status(500).json({ error: err.message });
46  }
47});

Create a Cloud Function named purchaseLabel. It accepts the rate_id (from the rate quote), shipFrom and shipTo addresses, and orderId (to link the label to the Firestore order). Call ShipEngine POST /v1/labels/rates/{rate_id} to purchase the label for the selected rate. ShipEngine charges the carrier account for the label cost. The response includes label_id, tracking_number, label_download.pdf (URL to the PDF label), label_download.png (URL to PNG preview), and shipment_cost. Write this to Firestore orders/{orderId}: set shippingLabel.trackingNumber, shippingLabel.labelPdfUrl, shippingLabel.carrier, shippingLabel.service, shippingLabel.cost, shippingLabel.purchasedAt. Return the label URL and tracking number to FlutterFlow.

On your order detail page, add a Create Shipping Label button visible only for orders without a label yet. The button opens a Bottom Sheet with a shipping form: weight TextField, dimensions TextFields (length × width × height), and the destination address (pre-filled from the order if available). Add a Get Rates button that calls the validateAddress function first, then getRates with the form inputs. Bind the results to a ListView of rate options. Each rate row has a Select button. On Select, show a Confirm Shipment dialog showing carrier, service, cost, and estimated delivery. On Confirm, call purchaseLabel. On success, show a Bottom Sheet with the tracking number and a Download Label button that calls Launch URL on the label PDF URL.