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.
npx skills add narpatsinghpurohit/tstack --skill understanding-codebasegit clone --depth 1 https://github.com/narpatsinghpurohit/tstackWrote 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.
[](https://agentmods.dev/skills/narpatsinghpurohit/tstack/understanding-codebase)<a href="https://agentmods.dev/skills/narpatsinghpurohit/tstack/understanding-codebase"><img src="https://agentmods.dev/badge/skills/narpatsinghpurohit/tstack/understanding-codebase/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.
<a href="https://agentmods.dev/skills/narpatsinghpurohit/tstack/understanding-codebase"><img src="https://agentmods.dev/badge/skills/narpatsinghpurohit/tstack/understanding-codebase.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00070 | $0.01970 |
| Opus 5.5 | $0.00028 | $0.00788 |
| Sonnet 5.5 | $0.00014 | $0.00394 |
| Haiku 4.5 | $0.00007 | $0.00197 |
Grade A, and why
understanding-codebase 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 1mo 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.
How it starts
The opening of the file, as written. The whole thing — 173 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Project Guide
Tech stack
| Layer | Technology |
|---|---|
| Monorepo | Turborepo + Bun workspaces |
| Backend | NestJS, Mongoose, MongoDB |
| Frontend | React + Vite, TanStack Router, TanStack Query, Zustand |
| UI | Tailwind CSS + shadcn/ui |
| Validation | Zod (shared between frontend and backend) |
| Auth | JWT (access + refresh tokens, Bearer header), Argon2 |
| Linting | Biome (replaces ESLint + Prettier) — config at root biome.json |
| Testing | Jest (backend + mobile), Vitest + React Testing Library + MSW (web), Jest + RNTL (mobile) |
| Mobile | React Native CLI, React Navigation, NativeWind |
Monorepo layout
project/
├── apps/
│ ├── api/ # NestJS backend
│ │ └── src/
│ │ ├── core/ # Auth, database, logging infrastructure
│ │ ├── common/ # Shared pipes, guards, filters, decorators, interceptors
│ │ ├── config/ # Env validation (Zod), config namespaces
│ │ └── modules/ # Feature modules (singular naming)
│ ├── web/ # React + Vite frontend
│ │ └── src/
│ │ ├── components/ # Shared UI (ui/ for shadcn, layout/ for shell)
│ │ ├── features/ # Feature modules (co-located, 3-file split)
│ │ ├── hooks/ # Global custom hooks
│ │ ├── lib/ # API client, utilities
│ │ ├── routes/ # TanStack Router route tree
│ │ └── stores/ # Zustand stores
│ └── mobile/ # React Native app
│ └── src/
│ ├── components/ # Shared mobile UI components
│ ├── features/ # Feature modules (co-located, 3-file split)
│ ├── hooks/ # Global custom hooks
│ ├── lib/ # API client, utilities
│ ├── navigation/ # React Navigation config (stacks, tabs, drawers)
│ └── stores/ # Zustand stores
├── packages/
│ └── shared/ # Zod schemas, types, constants
│ └── src/
│ ├── schemas/ # Zod validation schemas (single source of truth)
│ ├── types/ # Shared TypeScript interfaces
│ └── constants/ # Error codes, enums, route constants
├── specs/ # Feature specs (requirement, design, tasks)
├── turbo.json # Task pipeline
├── biome.json # Linting & formatting (root config)
└── tsconfig.base.json # Shared TypeScript config
What ships with it
3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 1mo ago First seen · 173 lines · 70 tokens per session scan A 754cdec54de8
understanding-codebase is a skill published in the GitHub repository narpatsinghpurohit/tstack (5 stars, last pushed 6mo ago), licensed MIT. It adds 70 tokens to every session and 1,970 once invoked, about $0.0003 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 2026-08-31.
Other skills, from other repositories
local-ai-agents
Build local-first AI agents that run entirely on a developer workstation with Microsoft Foundry Local and Qwen function-calling models. Covers Small Language Models (SLMs), the OpenAI-compatible local endpoint, sandboxed local tools, local RAG with Chroma, local MCP servers, hybrid cloud/local routing, and the…
systematic-debugging
Use when encountering any bug, test failure, or unexpected behavior, before proposing fixes.
next-cache-components-adoption
Turn on Cache Components in a Next.js app and resolve the blocking routes it surfaces. Use when the user wants to enable, adopt, or migrate to Cache Components, flip the cacheComponents flag, work through a flood of blocking-prerender / instant validation errors, run the cache-components-instant-false codemod, or…
chat-pet-sprite-creation
Use when creating or changing VS Code chat pet sprite art, sprite sheets, state animations, eye treatments, Stable/Insiders variants, or pet transitions under src/vs/workbench/contrib/chat/browser/widget/media/chatPet.
cpu-profile-analysis
Analyze V8/Chrome CPU profiles (.cpuprofile) and DevTools trace files (Trace-.json). Use when: profiling performance, investigating slow functions, comparing code paths, finding bottlenecks, analyzing timeToRequest, understanding call trees from sampling profiler data, analyzing layout/paint/rendering, investigating…
insight-error-page
Write or audit an insight-kind error page for the Next.js dev overlay. Use when creating a new errors/ .mdx page, auditing an existing one, or checking that a page matches the framework fix cards. Covers page structure, title alignment, FixCard cards with Copy prompt button, code snippets, terminology verification…