Build Your First Useful Tool

A vertical slice completes one narrow outcome from beginning to end. It includes enough interface, logic, and state for a real person to use it, but excludes every adjacent ambition. A meeting-note tool might accept text, extract decisions and owners, let a person correct them, and export a follow-up. It does not also need a company knowledge graph.

Choose a problem you have personally experienced and a result you can inspect. Your advantage as a beginner is proximity to the work. You can tell whether the output is useful even while an agent helps with implementation you could not yet write alone.

Before opening a coding agent, describe the user, trigger, input, outcome, constraints, and proof. Add explicit exclusions. If the agent must guess whether accounts, payments, collaboration, or mobile support are required, the project will expand faster than your ability to understand it.

Ask the agent to respond with a plan and a system map before it edits files. The plan should name the main screens, data shape, important files, risks, and test approach in plain language. Correct the model before paying the cost of implementing it.

Let the agent create the first complete version in bounded steps. After each step, ask what changed, why those files own the behavior, how to run it, and what remains unproven. Inspect the actual diff rather than relying only on the summary.

You do not need a line-by-line lecture. Focus on consequential boundaries: where input enters, where it is validated, where state lives, where secrets are read, which external actions can occur, and what happens when something fails.

A happy-path demo proves that one prepared example worked. A useful tool must also handle missing input, strange input, repeated actions, slow services, and a person changing their mind. Start with examples from the real workflow, including the cases that normally force manual cleanup.

Write expected behavior before testing. If a required field is empty, the interface should explain what is needed. If an external service fails, the user should know the action did not complete. If the same request is submitted twice, the system should avoid creating two consequential results.

A local build is useful for development, but another person cannot use localhost on your laptop. Create a preview or deployment with its own address and configuration. Then test that address as the user would, ideally in a clean browser session without relying on your developer state.

Say exactly what is live. 'The project builds locally,' 'the preview works,' and 'the production domain serves the new version' are different claims. Attach the URL, version, screenshot, and test result that support the claim you make.

Give the tool to one person who experiences the problem. Watch where they hesitate, what they assume, and what they try that you did not predict. Ask whether the tool changed the outcome, not whether the colors look nice.

Turn the observation into one bounded next change. Finishing, observing, and improving a small system teaches more than generating five abandoned prototypes.