Skip to content
Pulls API

Building a Price Tracker

Build a price tracker that monitors card prices across multiple TCGs. By the end, you’ll have a working application that tracks prices and alerts you to changes.

What You’ll Build

Section titled “What You’ll Build”
  • Fetch current prices for any card
  • Store historical price data
  • Detect significant price changes
  • Send alerts via Discord webhook

Prerequisites

Section titled “Prerequisites”
  • Node.js 18+
  • Pulls API key (Free tier works)
  • Discord webhook URL (optional, for alerts)

Setup

Section titled “Setup”

  1. Create project and install dependencies

    Terminal window
    mkdir price-tracker && cd price-tracker
    npm init -y
    npm install @pulls/sdk dotenv

  2. Configure environment

    .env
    PULLS_API_KEY=pk_live_your_key_here
    DISCORD_WEBHOOK_URL=https://discord.com/api/webhooks/...

  3. Initialize the SDK

    src/index.ts
    import { PullsAPI } from '@pulls/sdk'
    import 'dotenv/config'
    

    const pulls = new PullsAPI({
      apiKey: process.env.PULLS_API_KEY!
    })

Fetching Prices

Section titled “Fetching Prices”

Get current market prices for a card:

src/prices.ts
async function getCardPrice(cardId: string) {
  const card = await pulls.cards.get(cardId, {
    includePrices: true
  })


  return {
    id: card.id,
    name: card.name,
    tcg: card.tcg,
    prices: card.prices
  }
}


// Usage
const charizard = await getCardPrice('base1-4')
console.log(`${charizard.name}: $${charizard.prices.market}`)
// Output: Charizard: $420.00

Tracking Multiple Cards

Section titled “Tracking Multiple Cards”

Create a watchlist and fetch prices in bulk:

src/watchlist.ts
const watchlist = [
  'sv7-001',      // Pokemon
  'ltr-1',        // Lorcana
  'neo-1',        // One Piece
]


async function checkWatchlist() {
  const prices = await pulls.prices.list({
    cardIds: watchlist
  })


  return prices.map(p => ({
    cardId: p.cardId,
    market: p.market,
    change24h: p.change24h
  }))
}

Detecting Price Changes

Section titled “Detecting Price Changes”

Compare current prices against stored values:

src/alerts.ts
interface PriceRecord {
  cardId: string
  price: number
  timestamp: Date
}


const priceHistory: Map<string, PriceRecord[]> = new Map()


function detectSignificantChange(
  cardId: string,
  currentPrice: number,
  thresholdPercent: number = 10
): boolean {
  const history = priceHistory.get(cardId) ?? []
  if (history.length === 0) return false


  const previousPrice = history[history.length - 1].price
  const changePercent = ((currentPrice - previousPrice) / previousPrice) * 100


  return Math.abs(changePercent) >= thresholdPercent
}


function recordPrice(cardId: string, price: number) {
  const history = priceHistory.get(cardId) ?? []
  history.push({ cardId, price, timestamp: new Date() })
  priceHistory.set(cardId, history)
}

Sending Discord Alerts

Section titled “Sending Discord Alerts”

Notify when prices change significantly:

src/discord.ts
async function sendDiscordAlert(
  cardName: string,
  oldPrice: number,
  newPrice: number
) {
  const change = ((newPrice - oldPrice) / oldPrice) * 100
  const direction = change > 0 ? '📈' : '📉'


  await fetch(process.env.DISCORD_WEBHOOK_URL!, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
      embeds: [{
        title: `${direction} Price Alert: ${cardName}`,
        description: `Price changed ${change.toFixed(1)}%`,
        fields: [
          { name: 'Old Price', value: `$${oldPrice.toFixed(2)}`, inline: true },
          { name: 'New Price', value: `$${newPrice.toFixed(2)}`, inline: true },
        ],
        color: change > 0 ? 0x22c55e : 0xef4444
      }]
    })
  })
}

Complete Example

Section titled “Complete Example”

Tie it all together with a scheduled check:

src/index.ts
import { PullsAPI } from '@pulls/sdk'
import 'dotenv/config'


const pulls = new PullsAPI({ apiKey: process.env.PULLS_API_KEY! })


const watchlist = ['sv7-001', 'base1-4', 'ltr-1']
const priceHistory: Map<string, number> = new Map()


async function checkPrices() {
  console.log(`[${new Date().toISOString()}] Checking prices...`)


  const prices = await pulls.prices.list({ cardIds: watchlist })


  for (const price of prices) {
    const previousPrice = priceHistory.get(price.cardId)
    priceHistory.set(price.cardId, price.market)


    if (previousPrice) {
      const change = ((price.market - previousPrice) / previousPrice) * 100
      if (Math.abs(change) >= 10) {
        console.log(`ALERT: ${price.cardId} changed ${change.toFixed(1)}%`)
        // await sendDiscordAlert(...)
      }
    }
  }
}


// Check every 15 minutes
setInterval(checkPrices, 15 * 60 * 1000)
checkPrices() // Initial check

Next Steps

Section titled “Next Steps”
  • Add persistent storage (SQLite, Redis)
  • Track graded card prices with prices.graded
  • Use webhooks instead of polling (Pro+ plans)
  • Build a web dashboard with Next.js
Section titled “Related”