prd-to-spec

prd-to-spec is a skill for Claude Code from smallnest/pigo. It costs 77 tokens per session (3,035 once invoked), scanned A, original, MIT.

A process for turning a PRD, or Product Requirements Document describing what to build, into a technical specification describing how to build it. The result covers architecture, APIs, data, errors, and implementation agreements.

In plain words
What is it for?
Use it after creating or receiving a PRD to analyze the existing codebase, answer key design questions, produce a SPEC, review it, and save the final document.
Why use it?
It resolves technical ambiguity before coding and gives engineers or agents a shared plan to implement against.

Skill for Claude Code

Written for Claude Code: user-invocable in frontmatter.

Good fit Use it after creating or receiving a PRD to analyze the existing codebase, answer key design questions, produce a SPEC, review it, and save the final document.

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Install with agentmods
npx agentmods add skills/smallnest/pigo/prd-to-spec
Install

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.

Any agent
npx skills add smallnest/pigo --skill prd-to-spec
Clone the repo
git clone --depth 1 https://github.com/smallnest/pigo

Made for: Claude Code.

Wrote 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.

agentmods badge for prd-to-spec

README.md
[![agentmods](https://agentmods.dev/badge/skills/smallnest/pigo/prd-to-spec.svg)](https://agentmods.dev/skills/smallnest/pigo/prd-to-spec)
Your own site
<a href="https://agentmods.dev/skills/smallnest/pigo/prd-to-spec"><img src="https://agentmods.dev/badge/skills/smallnest/pigo/prd-to-spec.svg" alt="Measured on agentmods" height="20"></a>
Per session 77 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,035 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00077 $0.03035
Opus 5 $0.00039 $0.01517
Sonnet 5 $0.00015 $0.00607
Haiku 4.5 $0.00008 $0.00303

Measured 8d ago against content hash 18874c8970d0, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

prd-to-spec 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 8d 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.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

internal/builtinskills/skills/prd-to-spec/SKILL.md · 410 lines

How it starts

The opening of the file, as written. The whole thing — 410 lines — stays where its author put it; the contents beside it link to each section on GitHub.

prd-to-spec — PRD to Technical Specification

Transform a Product Requirements Document (PRD) into a detailed technical SPEC that an engineer or AI agent can implement against. The PRD says what to build; the SPEC says how to build it.


When to Use

  • A /prd has been generated and you need to bridge the gap to implementation
  • You want architecture decisions documented before coding starts
  • Multiple developers/agents will implement the feature and need a shared contract
  • You need to validate technical feasibility before committing to a PRD
  • You want to catch design issues early — before code is written

The Job

  1. Locate PRD — find or receive the PRD document
  2. Analyze context (optional) — if a codebase exists, scan it to understand current architecture, patterns, and constraints
  3. Ask clarifying questions — resolve technical ambiguities (max 3-5 questions)
  4. Generate SPEC — produce a structured technical specification
  5. Review — present to user for feedback and iteration
  6. Save — write final SPEC to agreed location

Step 1: Locate PRD

Find the input PRD in one of these ways:

Provide the PRD to convert:

A. File path (e.g., tasks/prd-priority-system.md)
B. GitHub Issue URL
C. Paste PRD content directly
D. Auto-detect: scan tasks/ directory for recent PRDs

If auto-detecting, list available PRDs and let the user choose:

Found PRDs in tasks/:
  1. tasks/prd-priority-system.md (2024-03-15)
  2. tasks/prd-user-auth.md (2024-03-10)

Which PRD should I convert? [1/2]

Step 2: Analyze Context (Optional)

Skip this step if no codebase exists yet (greenfield project). In that case, the SPEC will propose architecture from scratch based on the PRD requirements and clarifying questions.

If a codebase exists, scan it to understand:

  • Existing architecture — how the current system is structured
  • Tech stack — languages, frameworks, libraries already in use
  • Patterns — naming conventions, file organization, error handling approach
  • Database — current schema, migration tool, ORM
  • API style — REST/GraphQL/gRPC, authentication method, response format
  • Testing — test framework, coverage patterns, test utilities

Read the full file on GitHub · 410 lines

Changes

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.

  1. 8d ago First seen · 410 lines · 77 tokens per session scan A 18874c8970d0

Subscribe to this mod's changes

prd-to-spec is a skill published in the GitHub repository smallnest/pigo (425 stars, last pushed 8d ago), licensed MIT. It adds 77 tokens to every session and 3,035 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 2026-08-30.

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