A command for adding defined capabilities to an existing project, such as databases, Docker, or testing tools.

Use it to add MongoDB, PostgreSQL, Docker, Vitest, Playwright, and other listed project features.

It avoids manually wiring together the required files, dependencies, environment variables, and scripts, and can safely update features already installed.

How TheDecipherist/claude-code-mastery-project-starter-kit configures

Reuse

Borrowing it

Nothing to install: this file belongs to TheDecipherist/claude-code-mastery-project-starter-kit. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/TheDecipherist/claude-code-mastery-project-starter-kit/main/.claude/commands/add-feature.md

Clone the repo

git clone --depth 1 https://github.com/TheDecipherist/claude-code-mastery-project-starter-kit

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.

README.md

[![agentmods](https://agentmods.dev/badge/commands/thedecipherist/claude-code-mastery-project-starter-kit/add-feature/github.svg)](https://agentmods.dev/commands/thedecipherist/claude-code-mastery-project-starter-kit/add-feature)

Your own site

<a href="https://agentmods.dev/commands/thedecipherist/claude-code-mastery-project-starter-kit/add-feature"><img src="https://agentmods.dev/badge/commands/thedecipherist/claude-code-mastery-project-starter-kit/add-feature/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.

Your own site · 80×15

<a href="https://agentmods.dev/commands/thedecipherist/claude-code-mastery-project-starter-kit/add-feature"><img src="https://agentmods.dev/badge/commands/thedecipherist/claude-code-mastery-project-starter-kit/add-feature.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 17 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.

When invoked 3,243 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 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.

Model	Per session	Once invoked
Fable 5.1	$0.00017	$0.03243
Opus 5.5	$0.00007	$0.01297
Sonnet 5.5	$0.00003	$0.00649
Haiku 4.5	$0.00002	$0.00324

Measured 2mo ago against content hash f78667343b51, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

add-feature 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 2mo 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.

.claude/commands/add-feature.md · 350 lines

How it starts

The opening of the file, as written. The whole thing — 350 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Add Feature to Existing Project

Add capabilities (MongoDB, Docker, testing, etc.) to an existing starter-kit project after scaffolding. Idempotent — safely updates already-installed features to the latest version.

Arguments: $ARGUMENTS

Feature Definitions

The authoritative table of features that can be added to projects. Both /add-feature and /update-project reference these definitions.

Feature	Files (from $SOURCE)	Deps	DevDeps	Env Vars	Scripts	CLAUDE.md Rule
`mongo`	`scripts/db-query.ts`, `scripts/queries/example-find-user.ts`, `scripts/queries/example-count-docs.ts`	`strictdb@^0.1.0`, `mongodb@^6.5.0`	`tsx@^4.7.0`	`STRICTDB_URI`	`db:query`, `db:query:list`	Rule 3
`postgres`	`scripts/db-query.ts`, `scripts/queries/example-find-user.ts`, `scripts/queries/example-count-docs.ts`	`strictdb@^0.1.0`, `pg@^8.0.0`	`tsx@^4.7.0`	`STRICTDB_URI`	`db:query`, `db:query:list`	Rule 3
`docker`	Generated from templates (Dockerfile, docker-compose.yml)	—	—	—	—	Rule 10
`vitest`	`vitest.config.ts`	—	`vitest@^2.0.0`	—	`test:unit`, `test:unit:watch`, `test:coverage`	—
`playwright`	`playwright.config.ts`	—	`@playwright/test@^1.42.0`	—	`test:e2e`, `test:e2e:ui`, `test:e2e:headed`, `test:e2e:chromium`, `test:e2e:report`, `test:kill-ports`	Rule 4
`content`	`scripts/build-content.ts`, `scripts/content.config.json`	—	—	—	`content:build`, `content:build:id`, `content:list`	—

Step 0 — Resolve Source (Starter Kit)

Find the starter kit source directory:

If CWD has BOTH claude-mastery-project.conf AND .claude/commands/new-project.md → use CWD as $SOURCE
Else read ~/.claude/starter-kit-source-path → verify it still has both files
Else ask via AskUserQuestion: "Where is the starter kit cloned?" with a text input

Store as $SOURCE.

Step 1 — Parse Arguments

Read the full file on GitHub · 350 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.

2mo ago First seen · 350 lines · 17 tokens per session scan A f78667343b51

Subscribe to this mod's changes

add-feature is a command published in the GitHub repository TheDecipherist/claude-code-mastery-project-starter-kit (342 stars, last pushed 4mo ago), licensed MIT. It adds 17 tokens to every session and 3,243 once invoked, about $0.0001 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 2026-08-30.

Backend and APIs Containers DevOps and cloud

add-feature next to 6 commands from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
add-featureTheDecipherist/claude-code-mastery-project-starter-kit	Command	342	4mo ago	MIT	A	17	Claude Code
vios-architectureNVIDIA-AI-Blueprints/video-search-and-summarization	Command	2.0k	yesterday	Apache-2.0	A	42	Claude Code
banking-eda-validategonzalezpazmonica/pm-workspace	Command	51	5d ago	MIT	A	27	Claude Code
deploymentJustdvp/claude-code-templates	Command	7	25d ago	MIT	A	0	Claude Code
setup-projectMadAppGang/claude-code	Command	287	7mo ago	MIT	A	29	Claude Code
banking-eda-validategonzalezpazmonica/savia	Command	49	yesterday	MIT	A	27	Claude Code
migrate-azure-to-railwayAshikparvez89/larouex-fullstack-plugin	Command	3	24d ago	MIT	A	0	Claude Code

claude-code-mastery-project-starter-kit: Command for Claude Code