agentmods.dev

create-atomic-tool

create-atomic-tool is a skill for Claude Code from Eigenwise/atomic-agents. It costs 99 tokens per session (2,141 once invoked), scanned A, original, MIT.

A guide for building an Atomic Agents tool, which is a predictable operation an agent can call, such as a calculation or an API request. The tool defines validated input and output data and runs the operation.

In plain words
What is it for?
Use it to create tools, wrap an API, build a calculator or weather tool, access a database, or define typed success and failure results.
Why use it?
It removes the uncertainty around describing a tool to the language model while checking that its inputs and results have the expected shape.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the atomic-agents plugin — 7 skills, 2 agents shipped together

not rated 6.3krepo +5 8d ago A scan SkillSpector: warn 99 tokens original MIT

Good fit Use it to create tools, wrap an API, build a calculator or weather tool, access a database, or define typed success and failure results.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/eigenwise/atomic-agents/create-atomic-tool
View source ↗ Eigenwise/atomic-agents eigenwise.github.io
About the project

Atomic Agents is a lightweight, modular framework for assembling AI agents and applications from single-purpose components such as agents, tools, and context providers. It is for developers building maintainable agentic AI pipelines with reusable, composable parts and structured outputs. The catalogue entries provide agent skills, instructions, settings, and related development workflows for the framework.

Eigenwise/atomic-agents · 6,319 stars · on GitHub · eigenwise.github.io

Install

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.

Any agent
npx skills add Eigenwise/atomic-agents --skill create-atomic-tool
Clone the repo
git clone --depth 1 https://github.com/Eigenwise/atomic-agents

Made for: Claude Code.

Or install atomic-agents, the plugin that ships this one along with the rest of its 7 skills, 2 agents.

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.

agentmods badge for create-atomic-tool

README.md
[![agentmods](https://agentmods.dev/badge/skills/eigenwise/atomic-agents/create-atomic-tool/github.svg)](https://agentmods.dev/skills/eigenwise/atomic-agents/create-atomic-tool)
Your own site
<a href="https://agentmods.dev/skills/eigenwise/atomic-agents/create-atomic-tool"><img src="https://agentmods.dev/badge/skills/eigenwise/atomic-agents/create-atomic-tool/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.

agentmods 80×15 button for create-atomic-tool

Your own site · 80×15
<a href="https://agentmods.dev/skills/eigenwise/atomic-agents/create-atomic-tool"><img src="https://agentmods.dev/badge/skills/eigenwise/atomic-agents/create-atomic-tool.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 99 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,141 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. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 1 finding, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • medium Data Exfiltration · line 87
    Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.
    Fix: Verify the destination URL is trusted and necessary. Remove or replace with documented APIs. Ensure no secrets, tokens, or PII are transmitted.
How audits are shown
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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00099 $0.02141
Opus 5.5 $0.00040 $0.00856
Sonnet 5.5 $0.00020 $0.00428
Haiku 4.5 $0.00010 $0.00214

Measured 2mo ago against content hash b5c47926e2e1, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

create-atomic-tool 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-plugin/atomic-agents/skills/create-atomic-tool/SKILL.md · 201 lines

How it starts

The opening of the file, as written. The whole thing — 201 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Create an Atomic Agents Tool

A tool is a deterministic capability an agent can invoke. In Atomic Agents, every tool is a BaseTool[InSchema, OutSchema] subclass with a typed run() (and optional run_async()). The input/output schemas double as the tool's signature for the LLM and as Pydantic validation at runtime.

For deep material (MCP interop, distributing as a standalone package, advanced error patterns), the authority is ../framework/references/tools.md. This skill is the action-oriented path: clarify → write → verify.

When this fires vs the umbrella framework skill

  • This skill: the user is creating a specific tool — wrapping an API, building a calculator, scraping a page, querying a DB.
  • framework skill: questions about Atomic Agents in general, or the user is doing something other than authoring a tool.

Phase 1 — Clarify

Bundle into one message:

  1. What does the tool do? One sentence. This becomes the class docstring and feeds the LLM's tool description.
  2. Inputs and outputs. Names, types, units. If unclear, propose a schema pair and confirm.
  3. External dependencies. HTTP API? DB? Local computation only? If HTTP, what auth (API key env var, OAuth, none)?
  4. Sync, async, or both? If the rest of the project is async or the call is I/O bound, plan a run_async() alongside run().
  5. Failure modes. Rate limits, not-found, network errors — how should the agent see them? Default: typed failure output, not raised exceptions.

Skip any question already answered in context.

Phase 2 — Plan

Confirm the location and shape in one short block, then proceed:

  • File: <project>/tools/<tool_name>_tool.py (in-project tool — see ../framework/references/project-structure.md).
  • Schemas: <ToolName>Input, <ToolName>Output, optionally a typed failure shape.
  • Config: <ToolName>Config(BaseToolConfig) if the tool needs API keys, base URLs, timeouts, retries.
  • Sync vs async: pick one or both.
  • Error pattern: typed failure output (preferred) vs raise (only for programmer error).

Read the full file on GitHub · 201 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.

  1. 2mo ago First seen · 201 lines · 99 tokens per session scan A b5c47926e2e1

Subscribe to this mod's changes

create-atomic-tool is a skill published in the GitHub repository Eigenwise/atomic-agents (6,319 stars, last pushed 8d ago), licensed MIT. It adds 99 tokens to every session and 2,141 once invoked, about $0.0004 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.

Building agentsaiartificial-intelligencelarge-language-modellarge-language-modelsllmsopenai
Related

create-atomic-tool compared with skills from other repositories

create-atomic-tool next to 6 skills from other repositories
ModTypeStarsLast pushLicenceScanTokensWorks with
create-atomic-toolEigenwise/atomic-agentsSkill6.3k8d agoMITA99Claude Code
alfworld-device-operatorzjunlp/SkillNetSkill1.4k4d agoMITA93Claude Code, Codex
alfworld-inventory-managementzjunlp/SkillNetSkill1.4k4d agoMITA70Claude Code, Codex
alfworld-object-locatorzjunlp/SkillNetSkill1.4k4d agoMITA66Claude Code, Codex
scienceworld-measurement-takerzjunlp/SkillNetSkill1.4k4d agoMITA81Claude Code, Codex
scienceworld-threshold-evaluatorzjunlp/SkillNetSkill1.4k4d agoMITA69Claude Code, Codex
webshop-attribute-verifierzjunlp/SkillNetSkill1.4k4d agoMITA119Claude Code, Codex