write-a-prd

write-a-prd is a skill for Claude Code from craigcossairt/trellis. It costs 51 tokens per session (609 once invoked), scanned A, a copy of write-a-prd, MIT.

A product requirements document (PRD) writing workflow that turns a feature idea into a documented, agreed plan.

In plain words
What is it for?
It is for planning new features, identifying the modules to build or change, deciding what needs tests, and submitting the finished PRD to an issue tracker.
Why use it?
It removes guesswork by examining the existing code, asking detailed questions, and resolving design decisions before implementation begins.

Skill for Claude Code

Written for Claude Code: installed under .claude/.

Good fit It is for planning new features, identifying the modules to build or change, deciding what needs tests, and submitting the finished PRD to an issue tracker.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/craigcossairt/trellis/write-a-prd
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 craigcossairt/trellis --skill write-a-prd
Clone the repo
git clone --depth 1 https://github.com/craigcossairt/trellis

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 write-a-prd

README.md
[![agentmods](https://agentmods.dev/badge/skills/craigcossairt/trellis/write-a-prd.svg)](https://agentmods.dev/skills/craigcossairt/trellis/write-a-prd)
Your own site
<a href="https://agentmods.dev/skills/craigcossairt/trellis/write-a-prd"><img src="https://agentmods.dev/badge/skills/craigcossairt/trellis/write-a-prd.svg" alt="Measured on agentmods" height="20"></a>
Per session 51 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 609 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.
Origin 84% copy Near-identical to another mod 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 $0.00051 $0.00609
Opus 5 $0.00026 $0.00304
Sonnet 5 $0.00010 $0.00122
Haiku 4.5 $0.00005 $0.00061

Measured 8d ago against content hash 53985ca6fa61, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

write-a-prd 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

This is a copy

84% identical to write-a-prd — 24 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.

.claude/skills/write-a-prd/SKILL.md · 83 lines

How it starts

The opening of the file, as written. The whole thing — 83 lines — stays where its author put it; the contents beside it link to each section on GitHub.

This skill will be invoked when the user wants to create a PRD. You may skip steps if you don't consider them necessary.

  1. Ask the user for a long, detailed description of the problem they want to solve and any potential ideas for solutions.

  2. Explore the repo to verify their assertions and understand the current state of the codebase.

  3. Interview the user relentlessly about every aspect of this plan until you reach a shared understanding. Walk down each branch of the design tree, resolving dependencies between decisions one-by-one.

  4. Sketch out the major modules you will need to build or modify to complete the implementation. Actively look for opportunities to extract deep modules that can be tested in isolation.

    A deep module (as opposed to a shallow module) is one which encapsulates a lot of functionality in a simple, testable interface which rarely changes.

    Check with the user that these modules match their expectations. Check with the user which modules they want tests written for.

  5. Once you have a complete understanding of the problem and solution, use the template below to write the PRD. Submit it to the project's issue tracker.

Problem Statement

The problem that the user is facing, from the user's perspective.

Solution

The solution to the problem, from the user's perspective.

User Stories

A LONG, numbered list of user stories. Each user story should be in the format of:

  1. As an , I want a , so that

This list of user stories should be extremely extensive and cover all aspects of the feature.

Implementation Decisions

A list of implementation decisions that were made. This can include:

  • The modules that will be built/modified
  • The interfaces of those modules that will be modified
  • Technical clarifications from the developer
  • Architectural decisions
  • Schema changes
  • API contracts
  • Specific interactions

Read the full file on GitHub · 83 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 · 83 lines · 51 tokens per session scan A 53985ca6fa61

Subscribe to this mod's changes

write-a-prd is a skill published in the GitHub repository craigcossairt/trellis (4 stars, last pushed 18d ago), licensed MIT. It adds 51 tokens to every session and 609 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 84% identical to write-a-prd, differing in 24 lines, and is treated as a copy.

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