Stock Prices

SKILL.md

---
name: stock-prices
description: Query real-time stock prices and market data using the Stock Prices API. Responses are in TOON format—decode with @toon-format/toon. Use when fetching stock quotes, analyzing market data, or working with symbols like AAPL, NVDA, GOOGL, or any ticker symbols.
---

# Stock Prices API Skill

This skill helps you work with the Stock Prices API to fetch real-time market data and stock quotes.

## API Endpoint

**Base URL**: `https://stock-prices.on99.app`

**Primary Endpoint**: `/quotes?symbols={SYMBOLS}`

## Quick Start

Fetch stock quotes for one or more symbols (responses are in TOON format):

```bash
curl "https://stock-prices.on99.app/quotes?symbols=NVDA"
curl "https://stock-prices.on99.app/quotes?symbols=AAPL,GOOGL,MSFT"
```

Install the TOON decoder for parsing: `pnpm add @toon-format/toon`

## Response Format

The API returns **TOON** (Token-Oriented Object Notation) format—a compact, human-readable encoding that uses ~40% fewer tokens than JSON. This makes it ideal for LLM prompts and streaming.

### TOON Response Example

```
quotes[1]{symbol,currentPrice,change,percentChange,highPrice,lowPrice,openPrice,previousClosePrice,preMarketPrice,preMarketChange,preMarketTime,preMarketChangePercent,...}:
  NVDA,188.54,-1.5,-0.789308,192.48,188.12,191.405,190.04,191.8799,3.3399048,2026-02-11T13:49:16.000Z,1.771457,...
```

### Decoding TOON Responses

Use `@toon-format/toon` to parse responses back to JavaScript/JSON:

```typescript
import { decode } from "@toon-format/toon";

const response = await fetch("https://stock-prices.on99.app/quotes?symbols=NVDA");
const toonText = await response.text();
const data = decode(toonText);

// data.quotes is an array of quote objects
const quote = data.quotes[0];
console.log(`${quote.symbol}: $${quote.currentPrice}`);
```

The decoded structure matches JSON—same objects, arrays, and primitives.

## Available Data Fields

| Field                    | Type              | Description                           |
| ------------------------ | ----------------- | ------------------------------------- |
| `symbol`                 | string            | Stock ticker symbol                   |
| `currentPrice`           | number            | Current trading price                 |
| `change`                 | number            | Price change from previous close      |
| `percentChange`          | number            | Percentage change from previous close |
| `highPrice`              | number            | Day's high price                      |
| `lowPrice`               | number            | Day's low price                       |
| `openPrice`              | number            | Opening price                         |
| `previousClosePrice`     | number            | Previous day's closing price          |
| `preMarketPrice`         | number            | Pre-market trading price              |
| `preMarketChange`        | number            | Pre-market price change               |
| `preMarketTime`          | string (ISO 8601) | Pre-market data timestamp             |
| `preMarketChangePercent` | number            | Pre-market percentage change          |

## Usage Guidelines

### Multiple Symbols

Query multiple stocks by separating symbols with commas (max 50):

```bash
curl "https://stock-prices.on99.app/quotes?symbols=AAPL,GOOGL,MSFT,TSLA,AMZN"
```

### Error Handling

Always check for valid responses. Decode TOON before accessing data:

```typescript
import { decode } from "@toon-format/toon";

const response = await fetch("https://stock-prices.on99.app/quotes?symbols=NVDA");
const data = decode(await response.text());

if (data.quotes && data.quotes.length > 0) {
    const quote = data.quotes[0];
    console.log(`${quote.symbol}: $${quote.currentPrice}`);
}
```

### Price Analysis

Calculate common metrics:

```typescript
// Determine if stock is up or down
const isUp = quote.change > 0;
const direction = isUp ? "📈" : "📉";

// Calculate day's range percentage
const rangePct = ((quote.highPrice - quote.lowPrice) / quote.lowPrice) * 100;

// Compare current to open
const vsOpen = quote.currentPrice - quote.openPrice;
```

## Common Use Cases

### 1. Price Monitoring

```typescript
import { decode } from "@toon-format/toon";

async function checkPrice(symbol: string) {
    const res = await fetch(`https://stock-prices.on99.app/quotes?symbols=${symbol}`);
    const data = decode(await res.text());
    const quote = data.quotes[0];

    return {
        price: quote.currentPrice,
        change: quote.change,
        changePercent: quote.percentChange,
    };
}
```

### 2. Portfolio Tracking

```typescript
import { decode } from "@toon-format/toon";

async function getPortfolio(symbols: string[]) {
    const symbolString = symbols.join(",");
    const res = await fetch(`https://stock-prices.on99.app/quotes?symbols=${symbolString}`);
    const data = decode(await res.text());

    return data.quotes.map(q => ({
        symbol: q.symbol,
        value: q.currentPrice,
        dailyChange: q.percentChange,
    }));
}
```

### 3. Market Summary

```typescript
import { decode } from "@toon-format/toon";

async function marketSummary(symbols: string[]) {
    const res = await fetch(`https://stock-prices.on99.app/quotes?symbols=${symbols.join(",")}`);
    const data = decode(await res.text());

    const gainers = data.quotes.filter(q => q.change > 0);
    const losers = data.quotes.filter(q => q.change < 0);

    return {
        totalStocks: data.quotes.length,
        gainers: gainers.length,
        losers: losers.length,
        avgChange: data.quotes.reduce((sum, q) => sum + q.percentChange, 0) / data.quotes.length,
    };
}
```

## Popular Stock Symbols

### Tech Giants (FAANG+)

- `AAPL` - Apple
- `GOOGL` - Alphabet (Google)
- `META` - Meta (Facebook)
- `AMZN` - Amazon
- `NFLX` - Netflix
- `MSFT` - Microsoft

### High-Profile Stocks

- `NVDA` - NVIDIA
- `TSLA` - Tesla
- `AMD` - Advanced Micro Devices
- `INTC` - Intel
- `ORCL` - Oracle

### Indices

- `^GSPC` - S&P 500
- `^DJI` - Dow Jones
- `^IXIC` - NASDAQ

## Notes

- **Response format**: API returns TOON, not JSON. Use `decode()` from `@toon-format/toon` to parse.
- All prices are in USD
- Data updates in real-time during market hours
- Pre-market and after-hours data is available
- Timestamps are in ISO 8601 format (UTC)
- Maximum 50 symbols per request