rdkit-agent

name	rdkit-agent
description	Agent-first cheminformatics CLI powered by RDKit WASM for validating, converting, and analyzing chemical notation (SMILES, SMIRKS, InChI)
allowed-tools	Bash(which rdkit-agent), Bash(npm install *), Bash(npx rdkit-agent *), Bash(rdkit-agent *)

rdkit-agent Skill

Step 0 — Ensure rdkit-agent is available

Before running any command, check whether rdkit-agent is on the PATH:

which rdkit-agent

• If found (exit 0): proceed directly to the commands below.
• If not found (exit 1): install it into the workspace so the sandbox can reach it:

npm install rdkit-agent

Then invoke it via npx for the rest of the session (or until a global install is confirmed):

npx rdkit-agent version

Sandbox note: npm install writes to node_modules/ inside the current working directory, which is always writable. Network access to the npm registry is allowed by default. No elevated permissions are required. Do not attempt npm install -g — a global install writes outside the workspace and will be blocked in most sandboxed environments.

Why use this instead of Python rdkit

• ~1 ms per call (warm) vs 200–500 ms for a Python subprocess cold-start
• No Python runtime, no native build, no conda environment — pure Node.js
• WASM is initialized once per process (24 ms), then negligible overhead per call
• Structured JSON output by default when stdout is not a TTY
• All commands exit with machine-readable codes: 0=success, 1=validation failure, 2=usage error, 3=RDKit error

Cold start breakdown: ~110 ms total (Node.js startup ~85 ms + WASM init ~24 ms). Subsequent calls in the same process: ~1 ms.

Critical Invariants

1. Always validate before using chemistry strings

rdkit-agent check --smiles "c1ccccc1"
rdkit-agent check --smirks "[C:1][OH:2]>>[C:1]=O"

If overall_pass is false, read corrected_values or fix_suggestions before proceeding. Do not pass unvalidated SMILES to downstream commands.

2. Use --json for programmatic input

All commands accept a JSON payload — safer than shell quoting:

rdkit-agent descriptors --json '{"molecules":["CCO","c1ccccc1"]}'
rdkit-agent convert --json '{"input":"CCO","from":"smiles","to":"inchi"}'
rdkit-agent filter --json '{"smiles":["CCO","CC(=O)Oc1ccccc1C(O)=O"],"mw_max":200}'
echo '{"smiles":"CCO"}' | rdkit-agent descriptors --json -

3. Output is auto-JSON when not TTY

When you run rdkit-agent in a subprocess or pipe, output is JSON automatically. Use --output json to force it from a terminal.

4. Limit output size

rdkit-agent descriptors --smiles "CCO" --fields "MW,logP,TPSA"
rdkit-agent similarity --query "c1ccccc1" --targets "..." --top 5
rdkit-agent subsearch --query "[OH]" --targets "..." --limit 10

Command Reference

Command	One-liner
check	rdkit-agent check --smiles "CCO"
repair-smiles	rdkit-agent repair-smiles --input "C1CC"
convert	rdkit-agent convert --from smiles --to inchi --input "CCO"
descriptors	rdkit-agent descriptors --smiles "CCO"
balance	rdkit-agent balance --reactants "CCO,O=O" --products "CC=O,OO"
fg	rdkit-agent fg --smiles "CC(=O)Oc1ccccc1C(O)=O"
subsearch	rdkit-agent subsearch --query "[OH]" --targets "CCO,c1ccccc1"
fingerprint	rdkit-agent fingerprint --smiles "c1ccccc1" --type morgan --radius 2
similarity	rdkit-agent similarity --query "c1ccccc1" --targets "Cc1ccccc1,CCO" --threshold 0.5
scaffold	rdkit-agent scaffold --smiles "CC(=O)Oc1ccccc1C(O)=O"
filter	rdkit-agent filter --smiles "CCO,CC(=O)Oc1ccccc1C(O)=O" --lipinski
draw	rdkit-agent draw --smiles "c1ccccc1" --output benzene.svg --format svg
stats	rdkit-agent stats --smiles "CCO,c1ccccc1,CC(=O)Oc1ccccc1C(O)=O"
edit	rdkit-agent edit --smiles "[NH4+].[OH-]" --operation neutralize
rings	rdkit-agent rings --smiles "c1ccccc1"
react	rdkit-agent react --smirks "[C:1][OH]>>[C:1]Br" --reactants "CCO"
stereo	rdkit-agent stereo --smiles "CC(O)C(N)C"
atom-map	rdkit-agent atom-map add --smiles "CCO"
schema	rdkit-agent schema check
mcp	rdkit-agent mcp (starts MCP stdio server)
version	rdkit-agent version

Common SMILES Errors to Avoid

English name instead of SMILES

❌ benzene   → ✅ c1ccccc1
❌ toluene   → ✅ Cc1ccccc1
❌ aspirin   → ✅ CC(=O)Oc1ccccc1C(O)=O
❌ ethanol   → ✅ CCO
❌ caffeine  → ✅ Cn1cnc2c1c(=O)n(C)c(=O)n2C

Molecular formula instead of SMILES

❌ H2O  → ✅ O
❌ CO2  → ✅ O=C=O
❌ NH3  → ✅ N
❌ NaCl → ✅ [Na+].[Cl-]
❌ DMSO → ✅ CS(C)=O
❌ DMF  → ✅ CN(C)C=O
❌ THF  → ✅ C1CCOC1

LLM-generated artifacts

❌ "CCO"            → ✅ CCO   (strip quotes)
❌ SMILES: CCO      → ✅ CCO   (strip prefix)
❌ ```smiles\nCCO```→ ✅ CCO   (strip markdown)
❌ `CCO`            → ✅ CCO   (strip backticks)

Structural errors

❌ [Na+          → ✅ [Na+]       (unclosed bracket)
❌ CC(=O         → ✅ CC(=O)      (unclosed branch)
❌ c1cccc        → ✅ c1ccccc1    (unclosed ring)
❌ Na            → ✅ [Na+]       (bare metal)
❌ Cl-           → ✅ [Cl-]       (bare ion)

Use rdkit-agent repair-smiles to attempt automatic recovery.

WASM Limitations

One feature is unavailable in the standard @rdkit/rdkit WASM build. It returns a structured error with code: "NOT_SUPPORTED_IN_WASM" rather than silently failing:

Feature	Status
stereo --enumerate	Not available — use Python EnumerateStereoisomers
react	Available in @rdkit/rdkit >= 2022.03

MCP Server Mode

To expose all commands as MCP tools for Claude Desktop:

rdkit-agent mcp

Add to claude_desktop_config.json:

{
  "mcpServers": {
    "rdkit-agent": {
      "command": "rdkit-agent",
      "args": ["mcp"]
    }
  }
}

Node.js API

const { check, descriptors, convert, similarity, RDKIT_TOOLS, handleToolCall } = require('rdkit-agent');

const valid = await check({ smiles: 'CCO' });
if (!valid.overall_pass) throw new Error(valid.fix_suggestions.join(', '));

const desc = await descriptors({ smiles: 'CCO' });
// { MW: 46.07, logP: -0.18, TPSA: 20.23, ... }

Exit Codes

Code	Meaning
0	Success
1	Validation failure (overall_pass = false)
2	Usage error (bad arguments, missing input)
3	RDKit error (WASM not loaded, molecule parse failure)