Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add borhen68/SkillEngine --skill doubt-driven-developmentgit clone --depth 1 https://github.com/borhen68/SkillEngineWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/borhen68/skillengine/doubt-driven-development)<a href="https://agentmods.dev/skills/borhen68/skillengine/doubt-driven-development"><img src="https://agentmods.dev/badge/skills/borhen68/skillengine/doubt-driven-development/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/borhen68/skillengine/doubt-driven-development"><img src="https://agentmods.dev/badge/skills/borhen68/skillengine/doubt-driven-development.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00067 | $0.03849 |
| Opus 5.5 | $0.00027 | $0.01540 |
| Sonnet 5.5 | $0.00013 | $0.00770 |
| Haiku 4.5 | $0.00007 | $0.00385 |
Grade A, and why
doubt-driven-development scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
This is a copy
86% identical to doubt-driven-development — 85 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 285 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Doubt-Driven Development
Overview
The most dangerous mistake in software isn't writing bad code — it's being confidently wrong. Long coding sessions accumulate assumptions that quietly solidify into "facts" without anyone noticing. The agent that questions its own output is more reliable than the one that never doubts.
The doubt contract: Every non-trivial decision gets a fresh-context adversarial review before it stands. Not a friendly review — a biased-to-disprove review. The goal isn't to find reasons to approve; it's to find reasons to reject. If the decision survives cross-examination, it's worth keeping.
Real-world impact: Cognitive bias research shows that people who subject their own work to adversarial review catch 70% more errors than those who only seek confirmation. A 5-minute doubt check prevents the 2-hour debugging session that discovers your "obvious" assumption was wrong.
When to Use
A decision is non-trivial when at least one of these is true:
- It introduces or modifies branching logic
- It crosses a module or service boundary
- It asserts a property the type system or compiler cannot verify (thread safety, idempotence, ordering, invariants)
- Its correctness depends on context the future reader cannot see
- Its blast radius is irreversible (production deploy, data migration, public API change)
Apply the skill when:
- About to make an architectural decision under uncertainty
- About to commit non-trivial code
- About to claim a non-obvious fact ("this is safe", "this scales", "this matches the spec")
- Working in code you don't fully understand
When NOT to use:
- Mechanical operations (renaming, formatting, file moves)
- Following a clear, unambiguous user instruction
- Reading or summarizing existing code
- One-line changes with obvious correctness
- Pure tooling operations (running tests, listing files)
- The user has explicitly asked for speed over verification
If you doubt every keystroke, you ship nothing. The skill applies only to non-trivial decisions as defined above.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 285 lines · 67 tokens per session scan A c58f34cb2b40
doubt-driven-development is a skill published in the GitHub repository borhen68/SkillEngine (17 stars, last pushed 4mo ago), licensed MIT. It adds 67 tokens to every session and 3,849 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 86% identical to doubt-driven-development, differing in 85 lines, and is treated as a copy.
Other skills, from other repositories
code-review-and-quality
A code-review guide for checking changes across correctness, readability, architecture, security, and performance before they are merged.
code-simplification
A code-review and refactoring guide for making existing code easier to read while keeping its behavior unchanged. Refactoring means changing how code is organized without changing what it does.
doubt-driven-development
A development practice that puts an independent, fresh-context challenge in front of important coding decisions.
code-review-and-quality
Conducts multi-axis code review. Use before merging any change. Use when reviewing code written by yourself, another agent, or a human. Use when you need to assess code quality across multiple dimensions before it enters the main branch. Use when asked to review a diff or a pull request, even when the diff is pasted…
code-simplification
Simplifies code for clarity. Use when refactoring code for clarity without changing behavior. Use when code works but is harder to read, maintain, or extend than it should be. Use when reviewing code that has accumulated unnecessary complexity.
doubt-driven-development
Subjects every non-trivial decision to a fresh-context adversarial review before it stands. Use when you want every assumption cross-examined before proceeding, when stress-testing a plan for hidden failure modes, when correctness matters more than speed, when working in unfamiliar code, when stakes are high…