Creating valuable light weight tools
Creating customer focused proof of concept tools that are ready for production
About:
Creating a proof of concept tool built to generate professional guest invoices as PDF files using the Hostfully OpenAPI. In many vacation rental operations, invoices are a day one need, but the core product did not offer invoice generation. The tool is multi agency, pulls live booking data, generates a polished PDF, and supports multiple languages so customers can bill guests in their preferred format.
The problem: customers unable to create invoices
Multiple customers directly communicated a recurring problem what was thought to have a light weight solution. Customers regularly need to issue invoices for bookings but are without an in-product solution. Without a native invoice feature, teams resort to manual templates, copy paste workflows, or external tools that drift from what is actually in the reservation. That creates three recurring issues: inconsistent totals, wasted time, and a support burden when guests question the numbers.
The principles: reliable and customer ready
Make it customer ready from day one, even as a proof of concept.
Use real system data, not manual entry, so totals match the booking.
Keep it safe for multi agency use with per agency configuration and validation.
Generate professional output that a customer can send without editing.
Keep it fast and simple, fetch, preview, download.
Support localization so invoices can be issued in the languages customers need.
The insight: leverage the API
Invoices are a formatting problem, not a pricing problem. The pricing already exists in the system of record, so the fastest path to value is to pull authoritative booking and order data through the API, transform it into a clean set of line items, and render a consistent PDF. If the tool always fetches fresh data and standardizes invoice numbers per agency, it becomes reliable enough to use in real workflows, even before a full product build.
The solution: PDF builder
I built a multi agency invoice generator that integrates directly with Hostfully APIs and produces PDF invoices on demand.
User workflow:
Configure agency settings once
Users enter an API key, API URL, and agency UID through a settings screen. Credentials are validated before any invoice is generated.Enter lead details
Users paste a Lead UID, optionally add a guest company name, select a due date, and choose an invoice language.Fetch and preview orders
The tool retrieves lead, guest, property, agency, and order details through the API. It then displays a clear preview so the user can confirm dates, guest details, and totals.Generate and download the invoice
With one click, the tool posts the structured invoice payload to a backend endpoint, generates the PDF using PDFKit, and returns the PDF to download.
Key features:
Multi agency support with isolated settings per agency.
Multi language invoices, including English and French, with room to expand.
Automatic tax and VAT handling based on API data.
Credit handling so negative fees appear cleanly as credits.
Guest company name support for corporate billing.
Per agency invoice numbering using a consistent prefix plus sequence format.
Live data only, no caching, so invoices match the current reservation state.
Under the hood:
The frontend orchestrates the form, preview, and download flow.
The backend handles all Hostfully API calls, normalizes order data into invoice line items, and generates the final PDF.
A lightweight invoice counter system ensures invoice numbers remain unique per agency, backed by a file based store with a database backup.
The outcome:
This proof of concept closed an immediate customer gap by enabling invoice generation that previously required manual workarounds. It reduced time spent creating invoices, improved consistency between invoices and reservation totals, and provided a polished document customers could send to guests without editing. Most importantly, it validated real demand for an invoice feature while demonstrating that a small, API driven tool can be production ready enough for early customer use.
