How to Create a Custom GPT: Plan, Build, Test, Improve

A good custom GPT is a scoped tool with explicit instructions and a repeatable job. Start with the job, then use the current GPT creation interface and documentation available in your account.

Editorial note: GPT Growth Lab is independent. We do not claim firsthand product use unless explicitly stated. Offer terms can change, so verify current details before purchasing.

Define the job first

Write down who the GPT serves, what inputs it receives, what output it should produce, what it should refuse or escalate, and two or three examples of excellent responses.

Write behavioral instructions

Specify role, process, constraints, output format and how the GPT should handle uncertainty. Avoid contradictory instructions and unnecessary personality text that does not improve the task.

Add knowledge only when useful

Use reference material when the GPT needs stable source material specific to the job. Keep those sources maintained and avoid assuming uploaded information will remain current forever.

Test like a user

Try expected questions, vague questions, hostile inputs and requests outside scope. Tighten the instructions based on failures rather than adding random complexity.

Next useful reads

How to sell custom GPTs · GPT Creator Club alternatives · How to create a custom GPT