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 agentmods add instructions/toss/es-toolkit/agents-mdgit clone --depth 1 https://github.com/toss/es-toolkitWhat 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 | $0.02089 | $0.02089 |
| Opus 5 | $0.01045 | $0.01045 |
| Sonnet 5 | $0.00418 | $0.00418 |
| Haiku 4.5 | $0.00209 | $0.00209 |
Grade A, and why
es-toolkit AGENTS.md 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 yesterday.
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 — 152 lines — stays where its author put it; the contents beside it link to each section on GitHub.
es-toolkit LLM coding agent instructions
This file gives LLM coding agents the context they need to contribute to es-toolkit. Read it before making changes, and follow it together with .github/CONTRIBUTING.md (and its translations).
Project overview
es-toolkit is a modern, high-performance JavaScript utility library with a small bundle size and strong type annotations. It provides a curated set of utilities that are difficult to write with built-in JavaScript methods but are commonly needed in real-world projects, such as delay, windowed, keyBy, mapValues, camelCase, and toSnakeCaseKeys.
The library is split into two entry points:
es-toolkit— the strict, opinionated main library. Focused on the 85% use case with a simple interface, no complex options, and modern JavaScript semantics.es-toolkit/compat— a Lodash-compatible variant intended to make migration from Lodash easy. Compat is feature-complete; only behavior fixes against Lodash are accepted, not new functions.
es-toolkit is a zero-dependency library and ships with no runtime dependencies.
Development environment
- Primary environment: Node.js v24 (see
.nvmrcfor the exact version) - Recommended editor: Visual Studio Code
- Package manager: Yarn v4, installed via Corepack. See the package manager section in CONTRIBUTING.md for details.
To get started:
corepack enable
yarn install
Common commands:
yarn vitest run # Run all tests
yarn vitest run src/array/chunk # Run tests for a specific function
yarn lint # ESLint
tsc --noEmit # Typecheck
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.
- yesterday First seen · 152 lines · 2,089 tokens per session scan A 06a16c14cc06
es-toolkit AGENTS.md is an instructions file published in the GitHub repository toss/es-toolkit (11,316 stars, last pushed 2d ago), licensed MIT. It adds 2,089 tokens to every session, about $0.0104 per session on Opus 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.
Other instructions, from other repositories
codex AGENTS.md
AGENTS.md instructions for openai/codex, covering rust/codex-rs, the codex-core crate, code review rules, crate api surface and model visible context.
buildNext
Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).
next.js AGENTS.md
Instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.
vscode oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, applying the notice (cutover) and fallback chain (never fail the build).
spec-kit AGENTS.md
Instructions for github/spec-kit, covering agents.md, about spec kit and specify, quickstart — add a new integration in 5 steps, integration architecture and integrationmanifest — file tracking.
langchain AGENTS.md
Instructions for langchain-ai/langchain, covering global development guidelines for the langchain monorepo, corridor security analysis, project architecture and context, monorepo structure and development tools & commands.