sam-serra-plugins

A Claude plugin marketplace maintained by Sam Serra. Currently contains one plugin: agent-plumb-brief.

What's in this repo

Plugin	What it does	Version
agent-plumb-brief	Interview-style PRD writer for Sam's SDD framework. Grills you with one question at a time, refuses fuzziness, writes a clean markdown brief.	0.8.0

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Install — for non-developers (Cowork desktop app)

Three clicks, no terminal needed.

1. Click agent-plumb-brief.plugin in the file list above.
2. Click GitHub's "Download raw file" button (the icon next to the file size).
3. Once downloaded, double-click the file. Cowork will open an install dialog. Click Install.

After install, type / in any Cowork chat and pick write-brief to start a new PRD interview. Or just say "write a brief for [your feature]" and the skill will activate.

Updating

When a new version ships, you'll get a heads-up. Repeat the three steps above with the new file — Cowork will prompt to upgrade.

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Install — for developers (Claude Code CLI)

One command:

/plugin marketplace add samuelserraceo/sam-serra-plugins
/plugin install agent-plumb-brief@sam-serra-plugins

Replace samuelserraceo/sam-serra-plugins with the actual samuelserraceo/sam-serra-plugins once you create the repo on GitHub. Claude Code pulls from main by default and auto-detects updates.

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What agent-plumb-brief does

You pitch a feature idea in 1-3 sentences. The skill then:

1. Grills you one question at a time, each with a recommended answer — until every fuzzy word ("weekly", "active", "healthy", request_id, etc.) is pinned to a concrete rule.
2. Surfaces contradictions in real time. If you say "just for my 30 employees" early and "for our customers' employees too" later, it stops, quotes both back, forces you to pick one.
3. Runs four quality checks in chat before writing the brief — fuzzy words defined, acceptance criteria fireable on a preview deploy, output example + mockup attached, no contradictions between sections.
4. Writes a markdown PRD to your Cowork outputs folder. The PRD is concrete enough that another engineer or LLM could just build it without follow-up questions.

Built on top of Matt Pocock's grill-me methodology, with an 11-section output template designed for Sam's spec-driven development pipeline.

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Repo layout

sam-serra-plugins/
├── .claude-plugin/
│   └── marketplace.json      ← Claude Code marketplace manifest
├── plugins/
│   └── agent-plumb-brief/            ← plugin source (skills, references, manifest)
│       ├── .claude-plugin/plugin.json
│       ├── skills/write-brief/...
│       └── README.md
├── agent-plumb-brief.plugin          ← packaged bundle for Cowork (Option 1 install)
└── README.md                 ← this file

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Troubleshooting

"Plugin validation failed" on install. Make sure you downloaded the raw file, not GitHub's HTML preview of the file. The .plugin file should be ~32 KB. If you see a few KB of HTML instead, repeat step 2 making sure you click the raw-download button.

Two write-brief entries in the slash menu after install. You may have installed both the .plugin and a separate .skill file in the past. Go to Customize → Personal skills, remove the standalone write-brief, keep only the one under the agent-plumb-brief plugin.

/plugin marketplace add errors in Claude Code. Check that the repo is public (or that your Claude Code session has access to it). Marketplace add doesn't work for private repos on personal plans.

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Issues / suggestions

Open a GitHub issue on this repo, or message Sam directly.