AI Developer Toolkit
For developers who run agents every day
You still read every line the agent writes.That’s Level 3. There’s a Level 4.
100% of your code will be written by agents. The only question is which level you’re at. The free scorecard tells you in about eight minutes; the guides are the moves up — spec before diff, tests before review, a human before production — for Claude Code, Codex and Cursor.

You can execute bounded changes, but evidence and production feedback are still manual. Strengthen Test and Maintain before increasing autonomy.
- •Commit intent → spec → plan
- •Define acceptance evidence
- •Isolate Build work
- •Attach tests and review findings
- •Keep a human production gate
- •Add incident → intent feedback

Created by @jaskol_ski
26 years building web apps · 2 IPOs · AI Lecturer at SWPS University · Using Cursor since 2023, Claude Code and Codex since early beta · CTO at TasteRay (built with AI)
This is already happening at scale. The question is what your setup makes the agent prove before anything merges.
80%+of the lines Anthropic merged in May 2026 were written by ClaudeAnthropic · 2026-051,300PRs a week merged by Stripe’s agents, with no human-written codeStripe · 2026-02-19+24%more PRs merged by CLI-agent adopters, still holding four months inMicrosoft (arXiv 2607.01418) · 2026-07Used by engineering teams that ship with agents.
Engineering teams at these companies use Cursor, Claude Code, and Codex with AI Developer Toolkit.

At Level 3 the agent writes most of the code. Your job becomes reading it.
Three moves up the ladder: the brief, the proof, the closed loop
A request becomes
a contract the agent can meet.
intent.md says what done means, spec.md says how it must behave, plan.md says in what order. The agent starts from the same three files every time — not from whatever the last chat remembered.
# docs/intent.md
Outcome: Users can paginate through /api/users
Out of scope: Changing authorization
Acceptance evidence: API contract and integration tests
# docs/spec.md
Behavior: Cursor-based pagination with rate limits
Constraints: Preserve existing clients
# docs/plan.md
1. Extend the API contract
2. Implement the bounded change
3. Test, review and prepare release evidenceThe loop stops on proof,
not confidence.
Work runs in a sandbox or a worktree and ends when the tests pass, not when the agent says it is done. You review a diff with its evidence attached — which is what lets you stop reading every line.
{
"hooks": {
"Stop": [{
"hooks": [{
"type": "command",
"command": "npm run typecheck && npm test"
}]
}]
}
}
✓ Types checked
✓ Tests passed
✓ Acceptance evidence attachedProduction feedback becomes
the next brief.
A human still approves the release. What comes back — incidents, telemetry, review findings — is written into the next intent.md instead of dying in a chat log.
change: feat/api-pagination
artifacts:
- docs/intent.md
- docs/spec.md
- docs/plan.md
evidence:
tests: passed
review: approved
production_approval: required
feedback:
next_intent: pendingFiled by the job you’re doing. Start at your level.
Start on the Ladder — it is free — to see which level you are at. Then take the track for the tool you run and the workflows for the stage you are working in.

The Ladder
Levels 0–5, after Dan Shapiro: what changes at each level, what stays yours, and the one move up. Free to read, no account.

Getting started
The way of working in one sitting: set up repository context and ship your first bounded change with its evidence attached.

Method
The lifecycle and its principles: what an agent needs at Plan, Design, Build, Test, Deploy and Maintain, and where a human stays in the loop.

Cursor
The Cursor track: rules, scoped agent work, review evidence and the current capabilities — level by level, in the editor.

Claude Code
The Claude Code track: CLAUDE.md, hooks, subagents, MCP, isolation and release gates — from the terminal.

Codex
The Codex track: AGENTS.md, sandboxing, worktrees, approvals and evidence across the CLI, the app and the cloud.

Tool comparison
Cursor vs Claude Code vs Codex vs Copilot vs Windsurf: feature matrix, pricing analysis and migration guides.

Workflows
Context, planning, building, testing, shipping, operating and automating — the tool-neutral practice behind every track.

MCP & Skills
Which MCP servers and skills are worth adding, how to scope them, and how to keep them from eating your context.

Teams & Governance
Adopting agents across a team and governing what they may touch: permissions, review standards, rollout.

Cookbook
100+ numbered copy-paste recipes for React, Next.js, Vue, Node, Python, Go, Rust, databases, DevOps, error handling and mobile.

Which level is your workflow really at?
The free scorecard asks 25 questions about how your agents actually work through Plan, Design, Build, Test, Deploy and Maintain. About eight minutes, no account. You get your level on the ladder, the stage that caps it, and the one change that lifts it.
- L0
By hand
You write the code. AI is a search engine at best.
- L1
Assisted
Autocomplete and pasted snippets. The agent never sees the repo.
- L2
Paired
One agent, one bounded task, with a human watching each step.
- L3
Review manager
Agents implement bounded plans; you review every diff, test and risk note.
- L4
Spec manager
Humans own intent, specifications and gates; agents execute isolated plans.
- L5
Dark factory
Agents pull work behind policy and CI; humans set priorities and handle exceptions.
Is this for you?
For developers who can get an agent to write the code, and want the change to survive review, release and production without reading every line.
Perfect for you if...
- The agent wrote it, and you spent the week fixing what review found
- Your setup lives in chat history and nobody — including you — can reproduce it
- You use more than one of Claude Code, Cursor and Codex and want one way of working across them
- You have never run an agent unattended, because you would not trust the result
- You want to know your level, not guess it
Not for you if...
- You want prompt tricks, and nothing about how work is specified or reviewed should change
- You use AI for the occasional throwaway script
- You will not own review, risk or production approval
- You do not want any workflow files in the repository
One subscription. Every level, all three tools.
Find your level free. Then every guide for the climb — Claude Code, Codex and Cursor — plus the Setup Pack and all four books, in one plan.
Solo Developer
For a developer who wants to stop reading every line the agent writes.
then $19.99 per month
Cancel anytime
- The Setup Pack — CLAUDE.md, AGENTS.md, Cursor rules and MCP config generated for your stack ($49 on its own)
- 400+ guides and 100+ recipes for Claude Code, Codex and Cursor, each showing when it was last updated
- All four books — 348 chapters, EPUB & PDF, English and Polish ($159 at list price)
- A spec before the diff and tests before the review — the same order in all three tools
- The Level 3 → 4 patterns: sandboxes, stop hooks and verification gates that let you stop reading every line
- Migration playbooks from Copilot or a plain IDE into the same way of working
- The Discord for questions, and a public GitHub repo for reporting a mistake you found
Team
One level for the whole team, inherited on day one.
then $199.99 per month
Cancel anytime
- Everything in Solo Developer, for every engineer
- Unlimited seats — by email domain, or by named address for teams spread across domains
- Shared brief templates, repository context and verification gates for every seat
- All four books for every seat — EPUB & PDF
- One company invoice with VAT
- Direct email support from the author
Enterprise
An audit of where your teams really are, a measured pilot — and someone accountable for adoption.
unlimited seats
- Everything in Team, unlimited seats
- An audit of how each team actually works with agents, across Plan, Design, Build, Test, Deploy and Maintain
- The brief chain installed: intent, spec, plan, repository instructions and CI evidence
- Hands-on workshops plus a pilot team, with adoption measured from day one
- A pilot under least-privilege tools, human production approval and incident feedback
- White-label or on-premise? Ask on the intro call.
- Delivered personally by the author
Created by @jaskol_ski
26 years building web apps · 2 IPOs · AI Lecturer at SWPS University · Using Cursor since 2023, Claude Code and Codex since early beta · CTO at TasteRay (built with AI)
The math
It pays for itself in 13 minutes.
Every guide is meant to save you more than that in one sitting. If one doesn’t — 30-day money-back guarantee on a first purchase.
How we compare
| Free YouTube | Official Docs | AI Developer Toolkit | |
|---|---|---|---|
| Content | Scattered, often outdated | Feature reference only | 400+ guides, Levels 0–5 |
| Freshness | Recorded once | Release notes only | Every guide shows when it was last updated |
| Path | Figure it out yourself | No guidance | A level to find, a rung to climb |
Content
- Free YouTube: Scattered, often outdated
- Official Docs: Feature reference only
- AI Developer Toolkit: 400+ guides, Levels 0–5
Freshness
- Free YouTube: Recorded once
- Official Docs: Release notes only
- AI Developer Toolkit: Every guide shows when it was last updated
Path
- Free YouTube: Figure it out yourself
- Official Docs: No guidance
- AI Developer Toolkit: A level to find, a rung to climb

Move the whole team up a level.
One brief, one review standard and one release gate for everyone, in every repo — Claude Code, Cursor or Codex. Either as a shared-seat subscription, or installed in your own repositories in a half-day workshop.
Team
Every guide for every engineer — one price, one invoice.
unlimited seats — email domain or named addresses
- Everything in Solo Developer, for every teammate
- Shared repository context for Claude Code, Cursor and Codex
- All four books (EPUB & PDF) for every seat
- Direct email support from the author
Team Enablement Workshop
A hands-on half-day that installs the shared brief and the gates in your own repositories.
half-day, live · up to 15 developers
- Live, hands-on session on your own repositories
- intent.md → spec.md → plan.md templates plus repository instructions
- The verification, review and production gates the team keeps afterwards
- 3 months of the Team plan for attendees included
Just for you?

Turn agent pilots into a factory you can measure.
We audit how each team actually works with agents, install the brief and evidence chain, then run one bounded pilot with human gates. Adoption and outcomes are measured from day one, so the board reads numbers, not anecdotes.
Audit + Implementation
Diagnosis, the brief chain, hands-on workshops and one pilot with its outcomes measured.
- Everything in the AI Engineering Audit
- Canonical intent, spec and plan artifacts plus repository instructions
- 3–4 hands-on workshops + a pilot with 1–2 teams
- Weekly office hours through the rollout
- Outcome metrics: cycle time, review corrections, regressions and incidents
- Least-privilege tools, CI evidence and human production approval
- 12 months of AI Developer Toolkit access for the whole team
Adoption guarantee — if agreed usage targets aren’t met by week 8, you get an extra month of advisory free.
15 minutes, no obligation — we’ll look at how your team builds today.
AI Engineering Audit
Find the level each team is really at — and the one safeguard that moves it first.
- Interviews with developers and leads
- Review of repos, configs and AI-tooling telemetry
- Control map across Plan, Design, Build, Test, Deploy and Maintain
- Prioritized 90-day roadmap: the next safeguard, team by team
- Executive readout for leadership
100% credited toward Audit + Implementation.
Ongoing Advisory
The tools change. Your operating controls keep up.
- Two office-hours sessions per month with your leads
- Async support between sessions
- Monthly briefing: what changed in the tools, what to adopt
- Continuous tuning of repository context, agent policy and CI gates
Who delivers
Every engagement is delivered personally by Michał Jaskólski — 26 years in software, 2 IPOs, CTO, author of The AI Engineering Handbook and the 400+ guides on this site.
The math
For a 25-developer team the flagship works out to about $67 per developer per month over a year. What it buys is a measured change in how the team ships — cycle time, review corrections, regressions and incidents, tracked from day one.
What you actually get
The subscription, itemised.
Two of these are sold on their own, so their prices are checkable rather than claimed. The third is the subscription itself — nobody sells it separately, so it carries no number.
- The Setup Pack — repository context
- Your CLAUDE.md, AGENTS.md, Cursor rules and MCP config, generated for your stack, plus TESTING.md — shared repository context in about 20 minutes.
- Sold on its own for $49.
- $49Included
- The Book Library
- Four books, 348 chapters, EPUB and PDF — the cross-tool Handbook plus one deep book each on Cursor, Claude Code and Codex.
- Four titles listing at $39.99 each, rounded down. Both language editions are included.
- $159Included
- The Documentation Access
- Every guide for Levels 0–5, for Claude Code, Codex and Cursor — each showing when it was last updated.
- No separate price: this is the subscription itself, not an extra sold beside it.
- Not sold separately
- Downloadables
- $208
$208 of it, against $99.99 for a year.
What that access is worth is your own time: one hour of it costs more than two months of this.
Lifetime access closes 2026-10-01
After 2026-10-01 the lifetime plan is retired. Monthly and annual continue as normal. Everyone who already holds lifetime access keeps it.
Common questions
Refunds, invoices, seats — and the questions the page above provokes.
You could, and it would sound right. Ask one about Codex approval modes and there is a good chance you get `--approval-mode`, which is not a flag — the real one is `--ask-for-approval`, and its values are `untrusted`, `on-request` and `never`. Copy the invented one and Codex rejects the command outright — you do not get a wrong permission posture, you get an agent that will not start. What you are paying for is that this list of invented flags is checked against a named release, with the version written next to each entry — and that the guides show when they were last updated. It matters more the higher you run: an agent you watch at Level 2 gets corrected in a minute; an agent left unattended for twelve hours on an invented flag is twelve hours of nothing, discovered in the morning. We keep a list of the ones models keep inventing.
At scale they already write most of it. Anthropic reports that more than 80% of the lines merged into its codebase in May 2026 were written by Claude, and Stripe merges over 1,300 pull requests a week with no human-written code (Stripe, February 2026). Across the industry the share is lower: DX measured 51.9% AI-authored code on average across more than 400 companies in Q2 2026. The other half of the evidence matters just as much. in METR’s controlled study, experienced developers’ tasks took 19% longer with AI on their own repositories (2025), and Faros AI measured incidents per PR up 242.7% alongside the throughput gains (April 2026). Which set your team gets depends on what the agent has to prove before merge — that is what the levels measure.
You own intent, architecture, acceptance criteria, risk, production approval and exception handling. Agents can research, propose, implement, test and prepare evidence, but accountability does not move to the model. The workflow makes those human decisions explicit instead of hiding them inside a chat.
That is the most common reason people cancel, so start with one real change. Use the Setup Pack to add repository context, write intent.md, spec.md and plan.md for something you were going to build anyway, and run it in your tool. You get one change done the new way before you read anything else. If it still is not for you, the 30-day first-purchase refund covers it.
Tool fluency is Level 2 or 3, not a level of trust. Ask whether every request becomes a committed intent, spec and plan; whether the agent runs isolated; whether a PR carries its own evidence; whether incidents update the next plan. Where the answer is no, that is the guide to read — for the tool you run, at the release you run.
The levels are Dan Shapiro’s Five Levels (January 2026): from Level 0, where you write everything, to Level 5, the dark factory, where agents pull work behind policy and CI. Level 2 is one agent, one bounded task, with you watching. Level 3 is agents implementing plans while you review every diff. Level 4 is you owning the spec and the gates while agents run unattended. The six stages — Plan, Design, Build, Test, Deploy, Maintain — are what you do at each level: the scorecard asks about them to place you, and the guides show the stage practice that moves you up one rung.
A tutorial usually teaches one feature in one tool, as of the day it was recorded. Here the guides sit on the ladder, cover all three tools, and each shows when it was last updated — so you can see how old what you are reading is.
Yes. From your account page, and access runs to the end of the period you paid for.
Yes — 30 days from your first purchase, for any reason. Email support@developertoolkit.ai and we refund it; we won't argue with you about why. Applies to first-time purchases, as set out in the Terms.
You keep full access until the end of the period you've already paid for — the subscription simply doesn't renew. Your account stays in place, so you can pick up where you left off anytime. Any ebooks you've downloaded are yours to keep.
Yes. Payments are handled by Polar, our merchant of record, which issues an invoice for every charge with the applicable VAT or sales tax for your country. It lands in your inbox right after payment — ready to expense or pass to your accountant.
Unlimited seats for one flat price. Everyone with an email address on your company domain gets full access automatically, and teams spread across domains can add named addresses instead — no per-seat billing, no invites to manage. Need white-label or on-premise? Ask on an Enterprise intro call.
The 100+ recipes cover React, Next.js, Vue, Python, Node.js, Go and Rust, and the ladder itself does not care what language you write — the brief chain, the verification gates and the MCP setup are the same in every stack. The recipes make it concrete in yours.
Still have questions? Contact us

Find your level. Then climb one.
Seven days free, the whole library. Pick one real change and run it spec → diff → tests → review, and see what the agent leaves behind. Cancel anytime; 30 days to change your mind on a first purchase.
7-day free trial · Cancel anytime · 30-day money-back guarantee on a first purchase