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 agentmods add skills/peterblazejewicz/claude-plugins/spec-driven-developmentnpx skills add peterblazejewicz/claude-plugins --skill spec-driven-developmentgit clone --depth 1 https://github.com/peterblazejewicz/claude-pluginsWrote 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/peterblazejewicz/claude-plugins/spec-driven-development)<a href="https://agentmods.dev/skills/peterblazejewicz/claude-plugins/spec-driven-development"><img src="https://agentmods.dev/badge/skills/peterblazejewicz/claude-plugins/spec-driven-development.svg" alt="Measured on agentmods" 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 | $0.00082 | $0.02829 |
| Opus 5 | $0.00041 | $0.01414 |
| Sonnet 5 | $0.00016 | $0.00566 |
| Haiku 4.5 | $0.00008 | $0.00283 |
Grade A, and why
spec-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 4d 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.
How it starts
The opening of the file, as written. The whole thing — 239 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Spec-Driven Development
Overview
Write a structured specification before writing any code. The spec is the shared source of truth between you and the human engineer — it defines what we're building, why, and how we'll know it's done. Code without a spec is guessing.
When to Use
- Starting a new .NET solution or feature
- Requirements are ambiguous or incomplete
- The change touches multiple projects or assemblies in the solution
- You're about to make an architectural decision (hosting model, persistence layer, UI framework)
- The task would take more than 30 minutes to implement
When NOT to use: Single-line fixes, typo corrections, or changes where requirements are unambiguous and self-contained.
The Gated Workflow
Spec-driven development has four phases. Do not advance to the next phase until the current one is validated.
SPECIFY ──→ PLAN ──→ TASKS ──→ IMPLEMENT
│ │ │ │
▼ ▼ ▼ ▼
Human Human Human Human
reviews reviews reviews reviews
Phase 1: Specify
Start with a high-level vision. Ask the human clarifying questions until requirements are concrete.
Surface assumptions immediately. Before writing any spec content, list what you're assuming:
ASSUMPTIONS I'M MAKING:
1. This is an Avalonia 11 desktop app (not MAUI or WPF)
2. Target framework is .NET 8 (LTS), C# 12 language features
3. Persistence is EF Core 8 against SQLite for dev, PostgreSQL for prod
4. Testing with xUnit v3 + native `Xunit.Assert` (MSTest with its native `Assert` is acceptable per team standard)
5. MVVM via CommunityToolkit.Mvvm source generators
→ Correct me now or I'll proceed with these.
Don't silently fill in ambiguous requirements. The spec's entire purpose is to surface misunderstandings before code gets written — assumptions are the most dangerous form of misunderstanding.
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.
- 4d ago First seen · 239 lines · 82 tokens per session scan A e27e26184387
spec-driven-development is a skill published in the GitHub repository peterblazejewicz/claude-plugins (7 stars, last pushed 2mo ago), licensed MIT. It adds 82 tokens to every session and 2,829 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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