Custom GPT & OpenAI API development
ChatGPT development services for the enterprise — custom GPTs and assistants, OpenAI API and Assistants integration, function calling, RAG and fine-tuning, hardened for production.
Quick answerChatGPT development services build custom applications on OpenAI’s models and APIs — custom GPTs, ChatGPT-style assistants and copilots, retrieval-augmented answering over your content, function and tool calling into your systems, fine-tuning, evaluation and production hardening. This service owns the build intent; connecting OpenAI into your existing stack is covered by our OpenAI & ChatGPT Integration service.
What ChatGPT & OpenAI development covers
Custom GPTs & assistants
Purpose-built assistants and copilots with the right instructions, tools and guardrails.
OpenAI API & Assistants API
Responses / Assistants APIs, structured outputs and streaming, wired into your product.
Function & tool calling
Typed tools that let the model act in your systems safely, with approval for high-impact steps.
Retrieval-augmented answering
Grounding on your documents and data, with citations and permission-aware retrieval.
Cost & latency optimisation
Model routing, prompt and response caching, context management, batching and streaming.
Evaluation & hardening
Prompt-injection and jailbreak defence, evaluation suite, and monitoring after go-live.
Development or integration — which do you need?
| You want to… | Development (this page) | Integration |
|---|---|---|
| Create a new assistant or custom GPT | Yes | — |
| Design the RAG, tools and evaluation | Yes | — |
| Connect OpenAI into Salesforce / ServiceNow / M365 | — | Yes |
| Push AI output back into systems of record | — | Yes |
| Both, on one engagement | Common — we do them together | Common |
From prompt to production
Prototype
A working assistant on real data and tools in a few weeks.
Harden
Injection defence, evaluation harness, error handling, security review.
Integrate
Into your product or platform, with identity and audit.
Release
Environments, CI/CD, observability and a supported go-live.
Tune
Quality, latency and cost improved against real usage.
OpenAI development, delivered for the enterprise
Enterprise data terms
Enterprise API terms with no training on your data; Azure OpenAI where tenancy is required.
Evaluation-first
Every assistant ships with a versioned evaluation harness.
Same team, integration too
The engineers who build the assistant can also connect it into your systems.
Cost discipline
Cost-per-request and cost-per-user tracked from day one.
Responsible AI
Guardrails, human-in-the-loop and audit logging as standard.
You own it
Your code and configuration, in your repositories and environment.
- AWS
- DataStax
- Salesforce
- Snowflake
Also available for OpenAI
Connect OpenAI into your enterprise stack with OpenAI & ChatGPT Integration Services, or add dedicated OpenAI engineers to your team with Hire ChatGPT & OpenAI Developers.
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Content last reviewed: September 2026
Scaling this across the enterprise?
Our Enterprise AI Services practice brings generative AI, agents and LLMs to production at scale — with the governance, platform and operating model to keep them reliable, compliant and cost-controlled.
Building on ChatGPT or the OpenAI API?
Tell us what you want the assistant to do and we will come back with a proof-of-concept plan and timeline.
Talk to an AI specialist
Tell us where you are on your AI journey — a use case, a proof of concept, or a platform decision — and an AI consultant will come back with next steps and a rough shape for the engagement.