PolyHermes/polymarket-demo/src/createOrder.ts

//npm install @polymarket/clob-client
//npm install ethers
//Client initialization example and dumping API Keys

import { ApiKeyCreds, ClobClient, OrderType, Side, } from "@polymarket/clob-client";
import { Wallet } from "@ethersproject/wallet";

const host = 'https://clob.polymarket.com';
const funder = ''; //This is the address listed below your profile picture when using the Polymarket site.
const signer = new Wallet(process.env.PRIVATE_KEY || ""); //This is your Private Key. If using email login export from https://reveal.magic.link/polymarket otherwise export from your Web3 Application


//In general don't create a new API key, always derive or createOrDerive
const creds = new ClobClient(host, 137, signer).deleteApiKey();

//1: Magic/Email Login
//2: Browser Wallet(Metamask, Coinbase Wallet, etc)
//0: EOA (If you don't know what this is you're not using it)

const signatureType = 1; 
  (async () => {
    const clobClient = new ClobClient(host, 137, signer, await creds, signatureType, funder);
    const resp2 = await clobClient.createAndPostOrder(
        {
            tokenID: "87660119269436753918591605029528224889066452434179554814663664703244066132110", //Use https://docs.polymarket.com/developers/gamma-markets-api/get-markets to grab a sample token
            price: 0.37,
            side: Side.BUY,
            size: 5,
            feeRateBps: 0,
        },
        { tickSize: "0.01",negRisk: false }, //You'll need to adjust these based on the market. Get the tickSize and negRisk T/F from the get-markets above
        //Refer to the API documentation to locate a tokenID: https://docs.polymarket.com/developers/gamma-markets-api/fetch-markets-guide
        //Example token: 114304586861386186441621124384163963092522056897081085884483958561365015034812 ( Xi Jinping out in 2025, YES side )
        //{ tickSize: "0.001",negRisk: true },

        OrderType.GTC, 
    );
    console.log(resp2)
  })();