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/narpatsinghpurohit/tstack/spec-driven-developmentnpx skills add narpatsinghpurohit/tstack --skill spec-driven-developmentgit clone --depth 1 https://github.com/narpatsinghpurohit/tstackWhat 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 | $0.00075 | $0.00479 |
| Opus 5 | $0.00037 | $0.00239 |
| Sonnet 5 | $0.00015 | $0.00096 |
| Haiku 4.5 | $0.00007 | $0.00048 |
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 2d 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.
What it actually says
Spec-Driven Development
When to Use
Use this workflow when a feature:
- Touches 2+ apps (backend + web)
- Requires 3+ new modules/components
- Involves new data models or schemas
- Will span multiple coding sessions
- Has unclear requirements needing discovery
Decision Tree
Requirements clear + detailed? → Express mode (skip guided discovery) Requirements vague or complex? → Guided mode (structured discovery)
Phases
Phase 1: Requirements
Create specs/{feature}/requirement/REQUIREMENT.md
See references/requirement-gathering.md
Phase 2: Design
Create specs/{feature}/design/DESIGN.md
See references/design-creation.md
Phase 3: Tasks
Create specs/{feature}/tasks/TASK.md
See references/task-creation.md
Phase 4: Execution
Use feature-orchestrator or implement tasks directly.
See references/spec-execution.md
Resuming Work
When continuing a spec across sessions: See references/spec-resume.md
Updating Specs
When requirements change mid-implementation: See references/spec-update.md
References
What ships with it
7 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 2d ago First seen · 60 lines · 75 tokens per session scan A 6658f7521ad9
spec-driven-development is a skill published in the GitHub repository narpatsinghpurohit/tstack (5 stars, last pushed 5mo ago), licensed MIT. It adds 75 tokens to every session and 479 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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