How to Start Building with Kiro Spec-Driven Development
Kiro is an agentic IDE from AWS that converts a natural-language prompt into a structured spec — requirements, design, and task list — before it writes any code. It runs on macOS, Windows and Linux, and is available in a free preview tier.
Most AI coding tools jump straight from prompt to files, which is why you end up with an app that works in the happy path and falls apart on the edges. Kiro inserts a document step: you approve what it will build before it builds it. That is the whole idea, and it is either exactly what you want or extra friction.
What is spec-driven development?
A spec is three files. Requirements list user stories with acceptance criteria. Design covers architecture and data models. Tasks break the design into ordered implementation steps. Kiro generates all three from your initial prompt, and you edit them like documents.
Once the spec is approved, the agent implements tasks and can run hooks — automated actions like updating docs or running tests — when files change.
How do you start your first Kiro project?
- Install the Kiro app and sign in.
- Create a new folder or open an empty project.
- Describe the feature in plain language, including constraints like “no external database”.
- Read the generated requirements and fix anything wrong. This is the important step.
- Review the design and task list, then let the agent implement.
- Check each diff; reject or refine tasks that drift from the spec.
Skipping step four defeats the purpose. If the spec says users can sign up with email but you also need SSO, your app will not have SSO.
Is Kiro free?
Kiro launched as a free preview and transitioned toward paid tiers with usage-based agent limits. New accounts typically get free requests per month, with higher limits on paid plans. Given how often this changes, confirm on the pricing page inside the app rather than trusting a blog post.
Where does Kiro fit vs prompt-first agents?
| Approach | Best for |
|---|---|
| Spec-first (Kiro) | New features with real requirements |
| Prompt-first agents | Quick scripts and throwaway code |
| Autocomplete | Line-level edits in existing files |
For a 30-line Python utility, writing a spec is wasted effort. For a feature that touches auth, billing and a database, the spec pays for itself the first time requirements change.
What are the drawbacks?
It is slower to start. You spend the first 20-30 minutes reading documents instead of seeing code. Some developers find the three-file structure rigid and end up maintaining docs that drift from reality once the agent starts improvising.
Also worth knowing: the initial preview was tied to a limited set of model options, which frustrated teams standardized elsewhere.
Good fit: developers building features with clear acceptance criteria, especially solo builders who want a paper trail. Bad fit: people who want instant output with zero ceremony.
Quick Summary
- Kiro is an AWS agentic IDE that writes a spec before writing code.
- Specs have three parts: requirements, design, tasks.
- Available on macOS, Windows and Linux with a free tier.
- Review and edit the requirements before approving implementation.
- Best for feature work with real requirements, overkill for quick scripts.
