# Spec-First Build Docs: PRD, design system, architecture note, agents guide and readiness check

> A Markdown pack of the four documents to write before an agent builds anything, sized to the stakes: a PRD an agent can build from without inventing scope, the smallest design system that holds, a one-page architecture note with reversal costs, an agents guide with a project tree for Claude Code, Codex and Cursor, a weekly staleness pass and a nine-area readiness check.

- URL: https://paperchasewebb.ai/bots/marketplace/items/spec-first-build-docs-prd-design-system-architecture-agents-guide/
- Type: Prompt pack
- Category: Vibe coding
- By: PaperChaseWebb
- Works with: Claude Code, Codex, Cursor (named in the listing); Plain .md
- Price: $29 USD
- Difficulty: Intermediate
- Setup time: 30 min
- Time to result: A working PRD and agents guide in one sitting
- Format: Markdown (.md) file, spec-first-build-docs-prd-design-system-architecture-agents-guide.md
- Version: 1.0, updated 2026-10-26
- License: Personal and commercial use. Your specs are yours. Do not resell or republish this pack.

## What you end up with

Your coding agent carries out decisions you wrote down instead of guessing, the docs stay true as the project changes, and you know what is missing before real users arrive.

## What you get

- 10 sections in one .md file
- Three spec weights (one page, standard, full) and a one-minute way to pick
- A PRD template with a filled example, failure steps and a Decisions owed table
- A small design system template with color roles, component states and a never list
- A one-page architecture note with boundaries, failure behavior and a reversal cost table
- An agents guide template and a project tree for Claude Code, Codex and Cursor
- A weekly staleness pass with update triggers
- A nine-area production readiness check with a one-page verdict
- 12 prompts to draft, check and maintain the set

## Who it is for

Builders who start agent projects from a prompt and keep paying for the agent's guesses in rewrites.

## Tools needed

- Claude Code: reads CLAUDE.md and the docs folder
- Codex: reads AGENTS.md
- Cursor: reads the project rule that points to the guide
- You need: A coding agent such as Claude Code, Codex or Cursor
- You need: A project folder or repo

Cost to run: Free. Uses the coding agent you already have.

## Sample prompt: Find the guesses (Claude Code, Codex, Cursor)

```
Read this PRD [paste] as the agent that will build it.
List every place you would have to guess: a missing failure step, a feature that isn't testable, a data field with no sensitivity, a decision hidden in a sentence. For each, write the question I need to answer.
```

Run it before the first build prompt, not after.

## Sample prompt: Gather audit evidence (Claude Code, Codex)

```
For this system, go through the nine readiness areas. For each check, point to the file, setting or log that answers it, or write NO EVIDENCE.
Do not mark anything Pass. A person will grade it.
```

The builder gathers evidence. Someone else signs the verdict.

## Free preview of spec-first-build-docs-prd-design-system-architecture-agents-guide.md

````markdown
# Spec-First Build Docs: PRD, design system, architecture note, agents guide and readiness check

A PaperChaseWebb pack, version 1.0. Written for Claude Code, Codex and Cursor, and plain Markdown, so every template also works with any agent that reads files from your repo.

A coding agent builds from whatever context it has. When the scope, the look, the stack and the rules live only in your head, the agent fills the gaps with guesses, and you pay for those guesses later in rewrites. This pack gives you the four documents to write before the first prompt, a project tree that keeps them in front of the agent, a pass that keeps them true as the project changes, and an audit to run before real users arrive. It is sized to the stakes: a weekend experiment gets one page, a client build gets the full set.

It comes from how we start our own agent builds, plus three public breakdowns we studied and rebuilt in our own words. Every source is credited by link in `09-sources.md`.

## Files

| File | What it is for |
|---|---|
| 01-size-the-gate.md | Three weights of spec (one page, standard, full) and how to pick one in a minute |
| 02-prd.md | A product requirements template an agent can build from without inventing scope, with a filled example |
| 03-design-system.md | The smallest design system that keeps agent-built screens consistent: tokens, components, states, banned moves |
| 04-architecture-note.md | One page that fixes the expensive decisions: stack, data flow, boundaries, failure behavior, reversal cost |
| 05-agents-guide.md | The rules file that governs every agent in the repo, plus a project tree for Claude Code, Codex and Cursor |
| 06-staleness-pass.md | A short routine that keeps the four documents true, with triggers that force an update |
| 07-readiness-audit.md | A nine-area production readiness check graded from evidence, with a one-page verdict |
| 08-prompts.md | 12 prompts to draft, check and maintain the whole set |
| 09-sources.md | Every source we used, linked and credited |
````

## Worth knowing

- Tool file names and settings change often. Check the current Claude Code, Codex and Cursor docs for where instruction files live.
- The readiness check is a starting checklist, not a certification. Systems handling payments, health or personal data need the standards that apply to their field.

## Questions

**Do I need all four documents for a weekend project?** No. The pack sizes the gate to the stakes. A spike gets a one-page spec that answers the same four questions in a few lines each.

**How is this different from the AGENTS.md and CLAUDE.md starter files?** The starter files cover the rules file alone. This pack covers what the rules file points to: the PRD, design system and architecture note, how to keep them current, and an audit before launch.

## How to buy

$29 one time at https://paperchasewebb.ai/bots/marketplace/items/spec-first-build-docs-prd-design-system-architecture-agents-guide/. Stripe checkout, then an instant download page; the download link is also in your emailed receipt.

Seller: PaperChaseWebb Inc., mgmt@paperchasewebb.com