chem.compound

Look up a chemical compound by CID, common/IUPAC name, SMILES, or InChIKey. Returns CID, preferred name, IUPAC name, molecular formula, molecular weight, exact mass, SMILES, connectivity SMILES, InChI, InChIKey, XLogP, formal charge, the 10 most-common synonyms, a PubChem permalink, and source attribution. Data is sourced from NIH PubChem (public domain). Provide exactly one of cid, name, smiles, or inchikey.

price

$0.0010 USDC per call

method

GET/api/chem/compound

payment

x402 v2 · USDC on Base (EIP-3009) or Solana (SPL transfer)

auth

None. Sign the payment, retry with PAYMENT-SIGNATURE.

tier

Tier 0 — no paid upstream

Parameters

Name	Type	Description
`cid`	integer	PubChem Compound ID (CID), e.g. 2244 for aspirin. min 0 · max 2500000000
`name`	string	Common, trade, or IUPAC name, e.g. "aspirin" or "ibuprofen". min 1 chars · max 200 chars
`smiles`	string	SMILES structural notation, e.g. "CC(=O)Oc1ccccc1C(=O)O". min 1 chars · max 500 chars
`inchikey`	string	InChIKey (27-char hashed identifier), e.g. "BSYNRYMUTXBXSQ-UHFFFAOYSA-N". match ^[A-Z]{14}-[A-Z]{10}-[A-Z]$

Code samples

cURLbash

# 1. Probe with no auth → 402 envelope with PaymentRequirements
curl -sS 'https://2s.io/api/chem/compound?cid=0&name=example&smiles=example&inchikey=example'

# 2. Sign + retry with PAYMENT-SIGNATURE:
curl -sS 'https://2s.io/api/chem/compound?cid=0&name=example&smiles=example&inchikey=example' \
  -H 'PAYMENT-SIGNATURE: <base64-json-payload>'

# Or use the canonical runner (handles probe → sign → retry):
#   EVM_PRIVATE_KEY=0x... node --env-file=.env.local \
#     --experimental-strip-types scripts/x402-pay.ts \
#     'https://2s.io/api/chem/compound?cid=0&name=example&smiles=example&inchikey=example'

TypeScript / Node — @2sio/sdktypescript

import { TwoS } from '@2sio/sdk'

const client = new TwoS({
  privateKey: process.env.EVM_PRIVATE_KEY as `0x${string}`,
})

const result = await client.chem.compound({
  "cid": 0,
  "name": "example",
  "smiles": "example",
  "inchikey": "example"
})

console.log('endpoint:', result.endpoint)
console.log('cost:', result.costUsd, 'USDC')
console.log('tx:', result.settlement?.txHash)
console.log('data:', result.data)

Python — 2siopython

import os
from twosio import TwoS

client = TwoS(private_key=os.environ["EVM_PRIVATE_KEY"])

result = client.chem.compound(cid=0, name="example", smiles="example", inchikey="example")

print("endpoint:", result.endpoint)
print("cost:", result.cost_usd, "USDC")
print("tx:", (result.settlement or {}).get("tx_hash"))
print("data:", result.data)

MCP — Claude Desktop / AgentKit / any MCP hostjson

// 1. Add @2sio/mcp to your MCP host config (Claude Desktop example below).
//    EVM_PRIVATE_KEY funds x402 payments per call.

// claude_desktop_config.json
{
  "mcpServers": {
    "2sio": {
      "command": "npx",
      "args": ["-y", "@2sio/mcp"],
      "env": { "EVM_PRIVATE_KEY": "0x..." }
    }
  }
}

// 2. Once the server is running, agents call this tool via standard MCP:

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "chem.compound",
    "arguments": {
      "cid": 0,
      "name": "example",
      "smiles": "example",
      "inchikey": "example"
    }
  }
}

Discovery

/api/directory — full catalog of every endpoint
/openapi.json — OpenAPI 3.1 spec (per-op x-payment-info, x402Payment security)
/.well-known/x402 — machine-readable service descriptor for x402-aware crawlers
/.well-known/mcp/server-card.json — MCP SEP-1649 server card
/llms.txt — plain-text manifest for LLM ingestion

2s.io is x402-native. Every call is paid per-request from a USDC-funded EVM wallet on Base — no signup, no API keys, no monthly fees. Source code: github.com/2s-io/sdk.