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 buildmoonshot/skillpacks --skill spec-driven-developmentgit clone --depth 1 https://github.com/buildmoonshot/skillpacksWrote 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/buildmoonshot/skillpacks/spec-driven-development)<a href="https://agentmods.dev/skills/buildmoonshot/skillpacks/spec-driven-development"><img src="https://agentmods.dev/badge/skills/buildmoonshot/skillpacks/spec-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/buildmoonshot/skillpacks/spec-driven-development"><img src="https://agentmods.dev/badge/skills/buildmoonshot/skillpacks/spec-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 | $0.00066 | $0.00461 |
| Opus 5.5 | $0.00026 | $0.00184 |
| Sonnet 5.5 | $0.00013 | $0.00092 |
| Haiku 4.5 | $0.00007 | $0.00046 |
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 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.
What it actually says
Spec-Driven Development
For substantial work, write a short spec and agree on it before writing code. The design decisions are cheapest to change as text, before they're encoded across a dozen files.
Write the spec first
Keep it short — a focused page, not a document. Cover:
- Goal — what this needs to accomplish, in one or two sentences. What does "done" look like?
- Approach — the high-level shape: the main pieces, where they live, how data flows. Enough that someone could predict the file structure.
- Key decisions — the choices that matter, each with a one-line rationale: data model, the library or pattern picked, API shape, where state lives. Note the alternatives you rejected and why.
- Edge cases & failure modes — the inputs and conditions that will break a naive version (empty, concurrent, error, large, malicious). How each is handled.
- Out of scope — what this deliberately does not do, so scope doesn't creep mid-build.
Get alignment, then build
Present the spec and confirm direction before implementing. A wrong assumption caught in the spec costs one sentence; caught after implementation it costs a rewrite. Once agreed, the spec becomes the checklist you build and verify against.
Match the effort to the work
This is for substantial, multi-file, or hard-to-reverse work. A one-file change doesn't need a spec — that's what lightweight planning is for. Don't turn every task into a design doc; reserve this for when the design genuinely carries risk.
Why this matters
The most expensive mistakes are architectural — chosen early, discovered late, and woven through everything by the time they surface. A short spec surfaces those decisions while they're still one paragraph to change, and turns implementation into execution against a plan instead of design-by-accident.
What ships with it
1 file 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.
- 1mo ago First seen · 31 lines · 66 tokens per session scan A 386762076e99
spec-driven-development is a skill published in the GitHub repository buildmoonshot/skillpacks (2 stars, last pushed 4mo ago), licensed MIT. It adds 66 tokens to every session and 461 once invoked, about $0.0003 per session on Opus 5.5. 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.
Other skills, from other repositories
writers-pattern
Add a new platform writer module in src/writers/ that generates and writes agent config files for a supported platform. Each writer exports a function that accepts a config interface, creates directories (rules/, skills/, mcp configs), writes files with proper formatting and frontmatter, and returns string[] of…
caliber-testing
Writes Vitest tests following project patterns: tests/ directories, vi.mock() for module mocking with vi.hoisted() for test-time factories, global LLM mock from src/test/setup.ts, environment variable save/restore in beforeEach/afterEach, vi.clearAllMocks() lifecycle, and test file organization. Use when user says…
scoring-checks
Add a new deterministic scoring check in src/scoring/checks/ that evaluates config quality. Follows the Check[] return pattern, uses point constants from src/scoring/constants.ts, and integrates via filterChecksForTarget() in src/scoring/index.ts. Use when user says 'add scoring check', 'new check', 'modify scoring…
llm-provider
Adds a new LLM provider implementing LLMProvider interface with call() and stream() methods. Integrates with provider factory in src/llm/index.ts, config detection in src/llm/config.ts, and error handling via tracking and recovery. Use when adding a new model backend, integrating a third-party LLM API, or extending…
adding-a-command
Creates a new CLI command following the Commander.js pattern in src/commands/. Handles command registration in src/cli.ts, telemetry tracking via tracked() wrapper, and option parsing. Use when user says add command, new CLI command, create subcommand, or adds files to src/commands/. Do NOT use for modifying existing…
setup-caliber
Sets up Caliber for automatic AI agent context sync. Installs pre-commit hooks so CLAUDE.md, Cursor rules, and Copilot instructions update automatically on every commit. Use when Caliber hooks are not yet installed or when the user asks about keeping agent configs in sync.