The ChatGPT App SDK is new enough that experienced developers are still rare. If you're a UK business looking to build an App SDK integration, finding the right technical partner is the first challenge. This guide covers what to look for, what questions to ask, and how to evaluate proposals.
Why UK-based matters
For many businesses, the decision to use a UK-based developer is partly practical (timezone, communication ease) and partly contractual (data residency requirements, GDPR compliance, the ability to sign an NDA under English law). If your integration will handle customer data — and most production integrations do — having a developer who understands UK data protection obligations from the outset is worth paying for.
What to look for in an App SDK developer
Direct App SDK experience, not just ChatGPT or OpenAI API experience
The App SDK is a distinct framework from the OpenAI API. A developer who has built GPT wrappers, chatbots, or API integrations has relevant background knowledge, but App SDK development requires specific familiarity with the SDK client library, the DevMode workflow, the ChatGPT runtime's event model, and the App SDK registration process. Ask to see previous App SDK work, not just AI work generally.
Full-stack capability
An App SDK integration has both a front-end (the web application that renders in ChatGPT) and a back-end (the APIs your application calls to fetch data and process transactions). A developer who is strong on one side but not the other will either need to subcontract or will produce a weaker integration. Look for someone who can own the full stack, or a small team where both sides are covered.
Demonstrated understanding of the user journey, not just the technology
The best App SDK integrations succeed because the developer understood the business goal, not just the technical spec. A good App SDK developer should ask you about your customer's journey before they ask about your API. If the first questions are about your tech stack rather than your customer's workflow, that's a yellow flag.
Questions to ask before commissioning a build
- Have you built an App SDK experience end-to-end, from local development to production registration?
- Can you walk me through how you'd handle the DevMode setup and the first developer working session?
- How do you approach the App SDK event model — what are the key events you'd implement for our use case?
- How would you connect the App SDK experience to our existing [booking system / product catalogue / CRM]?
- What does your testing process look like before going to production?
- Have you handled user authentication or session management within an App SDK experience?
A developer with real App SDK experience will answer these questions fluently. Hesitation or generic answers ("we'd research that during the project") on the technical questions is a signal to probe further.
How to evaluate proposals
When comparing proposals from App SDK developers, the things that matter are:
- Scope clarity — does the proposal define exactly what user journeys will be supported, what components will be built, and what's out of scope?
- Fixed fee vs time and materials — for a defined scope, a fixed fee is lower risk for you. Time and materials works if you need a flexible scope, but budget for 20–40% overrun.
- DevMode access — will you be able to test the integration in DevMode during development, or only at the end?
- Deployment ownership — who registers the App SDK experience with OpenAI? Who handles updates and maintenance?
- Data handling commitments — if your integration handles customer data, the proposal should address how that data is stored, processed, and protected.
What a discovery session delivers
Before commissioning a full build, a discovery session is the lowest-risk way to validate that the App SDK is the right fit for your use case and that the developer you're considering is the right partner. A well-run discovery session should deliver:
- A clear mapping of your customer journey to App SDK components
- Identification of the back-end APIs your integration will need
- A technical feasibility assessment for any complex requirements
- A fixed-fee proposal for the full build
At app-sdk.com, our discovery session is £500 and runs for approximately 45 minutes over video call. If we proceed to a full build, the discovery fee is credited against the project cost.