Custom GPTDevelopment
A GPT configured for one job in your business, with your instructions, reference files and approved tools, rather than a blank chat window.
Custom GPT Development: what the work involves
Many teams already paste work into a general chatbot, and each person gets different results because each person writes a different prompt. One employee has a clever trick that never reaches anyone else. Confidential files get pasted into personal accounts, and nobody can say afterwards what the assistant was told to do.
We design a custom assistant around one clearly named task, such as drafting tender responses, checking product copy against brand rules or preparing a client brief. That means writing the system instructions, curating the reference files, deciding which actions it may call, and defining what a good output looks like. We build it on the OpenAI GPT platform when your team lives there, or as a standalone app on Claude or Gemini APIs when you need your own login, logging and branding. Before handover we run a fixed set of test prompts, including awkward ones, and record the outputs so changes can be compared.
Core features
Single-purpose design
One assistant, one job, with instructions that say what to do, what to refuse and what format to return.
Curated reference files
Style guides, templates, price lists and examples are prepared and uploaded so answers lean on your material.
Actions to your systems
Where useful, the GPT calls an API to look up an order, fetch a record or create a draft, within limits you set.
Test set and baselines
A written set of sample inputs and expected qualities lets you see whether an instruction change helped or hurt.
Hosted or standalone
Run it inside the GPT store for your workspace, or as an independent web app with your own login and usage logs.
Team handover guide
A short document explains what the assistant is for, how to phrase requests, and what it should not be trusted with.
What we get right before launch
Uploaded files can be exposed
A determined user may coax a GPT into revealing its instructions or files. We keep secrets, credentials and personal data out of the knowledge files entirely.
Platform dependence
Features and policies of a hosted GPT platform change. For critical work we build the logic as an API app so you can switch model vendors with little rework.
Quality drifts as models update
Provider updates can shift behaviour. We keep the saved test set and rerun it after notable model changes, so a regression is noticed early.
Tools and technology
- OpenAI
- Anthropic Claude
- Google Gemini
- Node.js
- Python
- FastAPI
- pgvector
Common questions, answered
Is a custom GPT the same as fine-tuning a model?
No. A custom GPT adds instructions, reference files and tools around an existing model. Fine-tuning changes the model's weights and is rarely needed. Most business tasks are better served by good instructions and retrieval.
Can staff outside our company use it?
Yes, if you publish it or build it as a standalone app with logins. For client-facing use we recommend the standalone route, since you control access, branding and the conversation logs.
Will it know our private documents?
Only those we provide to it. For larger or frequently changing collections, we connect it to a retrieval service instead of relying on uploaded files, which have size limits.
How do we know it keeps working well?
We hand over a test set you can rerun whenever instructions or the underlying model change, and suggest a short review of real conversations each month.
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Ready to start your Custom GPT Development project?
Tell us what you need and we will come back with a clear scope, timeline and the questions worth answering before any build starts.