Agent skill

Cas

Look up chemicals in CAS Common Chemistry (name, CAS RN, SMILES, InChI; ~500k compounds)

Apache-2.0Auto-check passedResearch & Science

Install Cas

skills CLI

$ npx skills add lamm-mit/scienceclaw --skill cas -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI

$ gh skill install lamm-mit/scienceclaw cas --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy

$ git clone --depth 1 https://github.com/lamm-mit/scienceclaw.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/cas .claude/skills/cas && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Paste into Claude Code

Install the "cas" agent skill from https://github.com/lamm-mit/scienceclaw/tree/main/skills/cas into .claude/skills/cas/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cas", then confirm the skill loads.

Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

$skill-installer

$skill-installer install https://github.com/lamm-mit/scienceclaw/tree/main/skills/cas

Type this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.

skills CLI

$ npx skills add lamm-mit/scienceclaw --skill cas -a codex

Project install goes to .agents/skills/; add -g for ~/.codex/skills/.

GitHub CLI

$ gh skill install lamm-mit/scienceclaw cas --agent codex

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/lamm-mit/scienceclaw.git skills-src && mkdir -p .agents/skills && cp -r skills-src/skills/cas .agents/skills/cas && rm -rf skills-src

Use ~/.agents/skills/ instead of .agents/skills for a personal install.

Codex skills documentation · loads skills from .agents/skills/

Paste into Codex

Install the "cas" agent skill from https://github.com/lamm-mit/scienceclaw/tree/main/skills/cas into .agents/skills/cas/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cas", then confirm the skill loads.

Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add lamm-mit/scienceclaw --skill cas -a cursor

Project install goes to .agents/skills/; add -g for ~/.cursor/skills/.

GitHub CLI

$ gh skill install lamm-mit/scienceclaw cas --agent cursor

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/lamm-mit/scienceclaw.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/skills/cas .cursor/skills/cas && rm -rf skills-src

Use ~/.cursor/skills/ instead of .cursor/skills for a personal install.

Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/

Paste into Cursor

Install the "cas" agent skill from https://github.com/lamm-mit/scienceclaw/tree/main/skills/cas into .cursor/skills/cas/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cas", then confirm the skill loads.

Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

gemini skills install

$ gemini skills install https://github.com/lamm-mit/scienceclaw.git --path skills/cas

--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.

skills CLI

$ npx skills add lamm-mit/scienceclaw --skill cas -a gemini-cli

Project install goes to .agents/skills/; add -g for ~/.gemini/skills/.

GitHub CLI

$ gh skill install lamm-mit/scienceclaw cas --agent gemini-cli

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/lamm-mit/scienceclaw.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/skills/cas .gemini/skills/cas && rm -rf skills-src

Use ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.

Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/

Paste into Gemini CLI

Install the "cas" agent skill from https://github.com/lamm-mit/scienceclaw/tree/main/skills/cas into .gemini/skills/cas/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cas", then confirm the skill loads.

Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

GitHub CLI

$ gh skill install lamm-mit/scienceclaw cas

Installs for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).

skills CLI

$ npx skills add lamm-mit/scienceclaw --skill cas -a github-copilot

Project install goes to .agents/skills/; add -g for ~/.copilot/skills/.

Manual copy

$ git clone --depth 1 https://github.com/lamm-mit/scienceclaw.git skills-src && mkdir -p .github/skills && cp -r skills-src/skills/cas .github/skills/cas && rm -rf skills-src

Use ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.

GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/

Paste into GitHub Copilot

Install the "cas" agent skill from https://github.com/lamm-mit/scienceclaw/tree/main/skills/cas into .github/skills/cas/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cas", then confirm the skill loads.

GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add lamm-mit/scienceclaw --skill cas -a opencode

OpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.

GitHub CLI

$ gh skill install lamm-mit/scienceclaw cas --agent opencode

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/lamm-mit/scienceclaw.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/skills/cas .opencode/skills/cas && rm -rf skills-src

Use ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.

OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/

Paste into OpenCode

Install the "cas" agent skill from https://github.com/lamm-mit/scienceclaw/tree/main/skills/cas into .opencode/skills/cas/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "cas", then confirm the skill loads.

OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

Facts

Skill name: cas
GitHub stars: 244
Token cost: ~504 tokens
SKILL.md length: 167 words
Files: 4 (incl. scripts, references)
Skills in repo: 85
Repo updated: Aug 21, 2026
First seen: Oct 7, 2026
Licence: Apache-2.0

At a glance

Look up chemicals in CAS Common Chemistry (name, CAS RN, SMILES, InChI; ~500k compounds)

Tasks that involve Drug discovery and cheminformatics
SKILL.md covers Overview, Usage, Parameters and Output, plus 1 more section
Runs Python scripts from its folder; calls python3; needs CAS_API_KEY

What it does

Cas is an agent skill from lamm-mit/scienceclaw. Look up chemicals in CAS Common Chemistry (name, CAS RN, SMILES, InChI; ~500k compounds)

Its SKILL.md is about 500 tokens, which your agent loads only when the skill is triggered. The skill folder holds 6 other files, including scripts and reference files (for example `references/cas-common-chemistry-api.md` and `scripts/cas_search.py`).

It sits in Research & Science, covering Drug discovery and cheminformatics. The licence is Apache-2.0.

When your agent uses it

Tasks that involve Drug discovery and cheminformatics

Example prompts

“/cas”

Requirements

Python 3
A credential in CAS_API_KEY

What it can do on your machine

Read from SKILL.md and the folder at commit ab9aba1. It shows what the files ask for, not the result of running them.

Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
Ships 2 files in scripts/ (Python), which the agent can run.
Shell commands in SKILL.md call:
- python3
From the folder's file list and the shell code blocks in SKILL.md.
Network
Links to these hosts (documentation or services it may open):
- cas.org
- commonchemistry.cas.org
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names these keys or tokens, usually read from environment variables:
- CAS_API_KEY
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Cas loads about 504 tokens when it runs, and up to ~1.3k if it reads all its reference files. Until then it costs about 23 tokens; SKILL.md has 167 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~23
When it runs · the whole SKILL.md, loaded when a task matches: ~504
With references · SKILL.md plus every file in references/, read only if the agent opens them: ~1.3k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); the scripts in this folder are not scanned.

SKILL.md

The full file from lamm-mit/scienceclaw at commit ab9aba1, republished under its Apache-2.0 licence (© lamm-mit). 167 words, ~504 tokens.

Download SKILL.mdSave it as .claude/skills/cas/SKILL.md (or your agent's skills folder). This skill also uses 3 other files; get the full folder from GitHub.

name: cas
description: Look up chemicals in CAS Common Chemistry (name, CAS RN, SMILES, InChI; ~500k compounds)

CAS Common Chemistry

Query CAS Common Chemistry for compound names, CAS Registry Numbers®, molecular formula, mass, SMILES, InChI, and experimental properties. Covers nearly 500,000 compounds (CC BY-NC 4.0).

API access: Request a free API key at https://www.cas.org/services/commonchemistry-api. The script works without a key for public endpoints; if CAS requires a key, set CAS_API_KEY or use ~/.scienceclaw/cas_config.json.

Overview

Search by compound name (supports trailing wildcard, e.g. aspirin*), CAS RN, SMILES, or InChI/InChIKey
Get detail: name, formula, mass, InChI, SMILES, experimental properties (e.g. melting point, density)
Reference: references/cas-common-chemistry-api.md

Usage

Search by name

bash

python3 {baseDir}/scripts/cas_search.py --query "aspirin"

Get detail by CAS Registry Number

bash

python3 {baseDir}/scripts/cas_search.py --cas "50-78-2"

Search with wildcard

bash

python3 {baseDir}/scripts/cas_search.py --query "atrazin*"

JSON output

bash

python3 {baseDir}/scripts/cas_search.py --query "caffeine" --format json

Parameters

Parameter	Description	Default
`--query`	Name, SMILES, or InChI (name supports trailing *)	-
`--cas`	CAS Registry Number (e.g. 50-78-2)	-
`--max-results`	Max search results	10
`--format`	summary, detailed, json	summary

Output

Summary: CAS RN, name, formula, molecular mass, SMILES
Detailed: Adds InChI, InChIKey, experimental properties, synonyms
JSON: Full API response

Notes

Request API access: CAS Common Chemistry API
Optional: set CAS_API_KEY or config file if CAS requires authentication

Files

SKILL.md and 3 other files (scripts, references) in skills/cas of lamm-mit/scienceclaw.

SKILL.md
references/cas-common-chemistry-api.md
scripts/__pycache__/cas_search.cpython-313.pyc
scripts/cas_search.py

Open the folder on GitHubat commit ab9aba1

Compare with similar skills

Cas next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Cas compared with similar skills
Skill	Stars	Used in	Tokens	Auto-check	Licence	Repo updated
Cas this skilllamm-mit/scienceclaw	244	—	~504	Automated safety check: Pass	Apache-2.0	1 mo ago
MolecodeAtomFlow-AI/MoleCode	305	—	~1.9k	Automated safety check: Pass	MIT	4 mo ago
Drug DiscoveryTommy-yw/RunbookHermes	546	1 repos	~2.3k	Automated safety check: Pass	MIT	4 mo ago
DiffDock Molecular DockingK-Dense-AI/scientific-agent-skills	48k	1 repos	~3k	Automated safety check: Notes	MIT	3 days ago
Biomedical Analysis Dispatchxjtulyc/MedgeClaw	617	1 repos	~2k	Automated safety check: Pass	None	7 mo ago
Edu Chem Reactionwy51ai/edulab	1.4k	—	~1.2k	Automated safety check: Pass	Apache-2.0	10 days ago

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Questions about Cas

What does Cas do?

Look up chemicals in CAS Common Chemistry (name, CAS RN, SMILES, InChI; ~500k compounds). Cas is an agent skill from lamm-mit/scienceclaw.

When should I use Cas?

Cas fits situations like: tasks that involve Drug discovery and cheminformatics.

How do I install Cas in Claude Code?

Run `npx skills add lamm-mit/scienceclaw --skill cas -a claude-code`. Or copy the skill folder (skills/cas in lamm-mit/scienceclaw) into .claude/skills/cas in your project. Claude Code loads it when a task matches its description.

How do I install Cas in Codex?

Run `npx skills add lamm-mit/scienceclaw --skill cas -a codex`. Or copy the skill folder (skills/cas in lamm-mit/scienceclaw) into .agents/skills/cas in your project. Codex loads it when a task matches its description.

Can I use Cas in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add lamm-mit/scienceclaw --skill cas -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/cas, .gemini/skills/cas, .github/skills/cas and .opencode/skills/cas in your project.

What does Cas need to run?

Going by SKILL.md and its folder, Cas needs Python for the scripts in its folder, the command-line tools its instructions call (python3) and credentials named CAS_API_KEY. Our summary lists: Python 3; A credential in CAS_API_KEY.

Does Cas access the network?

SKILL.md names 2 domains. As links in the text: cas.org and commonchemistry.cas.org. This is read from the text; nothing was executed.

Is Cas safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. The check reads SKILL.md only: the scripts in the folder are not scanned, so read them before running anything.

What licence does Cas use?

Cas is published under the Apache-2.0 licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Cas use?

About 504 tokens (SKILL.md is roughly 2k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 839 tokens, read only when the agent opens those files.

What are the alternatives to Cas?

Skills that share tags, products or a category with Cas: Molecode (AtomFlow-AI/MoleCode, 305 stars), Drug Discovery (Tommy-yw/RunbookHermes, 546 stars), DiffDock Molecular Docking (K-Dense-AI/scientific-agent-skills, 48k stars) and Biomedical Analysis Dispatch (xjtulyc/MedgeClaw, 617 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Cas?

lamm-mit (a GitHub user) maintains it in lamm-mit/scienceclaw, which has 244 GitHub stars. The repository holds 85 skills in this directory. The repository was last updated on August 21, 2026.

Source: lamm-mit/scienceclaw on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.

Install Cas

Facts

At a glance

What it does

When your agent uses it

Example prompts

Requirements

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

CAS Common Chemistry

Overview

Usage

Search by name

Get detail by CAS Registry Number

Search with wildcard

JSON output

Parameters

Output

Notes

Files

Compare with similar skills

Similar skills

More from lamm-mit/scienceclaw

Related

Questions about Cas