Level Up Your App: JustTCG API Now Includes 90-Day Market Analytics

That’s why we are thrilled to announce the rollout of a comprehensive suite of 90-day statistical data fields to the /cards endpoint. This major enhancement is live now and gives you a much deeper, quarterly view of a card's market performance, empowering you to build more accurate and intelligent TCG tools.

A Deeper Look: What’s New? #

We’ve added a set of powerful calculated metrics that give you an instant snapshot of a card’s stability, momentum, and trading range over the last three months. Here’s what you can now access for every card variant:

• 90-Day Price Change (**priceChange90d**): See a card's price movement in both percentage and absolute terms over the last quarter. Instantly know if a card is on an upward trajectory or cooling off.
• 90-Day Average, Min & Max Price (**avgPrice90d**, **minPrice90d**, **maxPrice90d**): Understand the full trading range and the central price point over a longer period, smoothing out single-day spikes or dips.
• 90-Day Volatility & Trend (**stddevPopPrice90d**, **trendSlope90d**): Quantify a card's price stability. The standard deviation (stddevPopPrice90d) shows how much the price has fluctuated, while the trend slope (trendSlope90d) indicates the overall market direction.
• Price in Range (**priceRelativeTo90dRange**): This simple but powerful metric (from 0 to 1) shows where the current price sits within its 90-day high-low range. A value near 1 means it's trading near its quarterly high; a value near 0 means it's near its low.

Putting the New Data to Work #

This isn’t just more data; it’s the foundation for smarter features. Here are a couple of ideas to get you started:

1. Build a “Stability Score”: For your users who treat their collection as an asset, you can now provide a risk assessment. Combine the stddevPopPrice90dwith the trendSlope90dto create a "Stability Score." A card with low volatility and a positive trend is a stable gainer, while a card with high volatility might be a riskier, high-reward asset. This is perfect for portfolio trackers and valuation tools.
2. Spot Seasonal & Long-Term Trends: Is a specific card’s price always dipping a month before it rotates out of standard play? Does a card see a consistent price increase every holiday season? With a 90-day view, you can start to identify these longer-term patterns that are invisible in 7-day or 30-day windows, helping your users make more informed buying and selling decisions.

A Note on Full Price History & Our Roadmap #

As you explore these new fields, you might notice that a full, point-by-point priceHistory90d JSON object is not part of this update. This was a deliberate choice.

Our primary commitment to you is a simple, reliable, and lightning-fast API. Adding a full 90-day historical data object for every single card variant is a massive architectural step that carries significant performance and scalability implications. We believe in rolling out new features responsibly to ensure the stability you depend on is never compromised.

We are taking the time to architect this full history feature correctly, guaranteeing it will be performant and backward-compatible with your existing integrations. In fact, providing full, extended price history is a top priority and a cornerstone feature planned for the next major version of our API (v2). We are hard at work on it and can’t wait to share more in the future.

Get Building Today #

These new 90-day analytics provide a powerful new lens through which to view the TCG market. They enable a more sophisticated analysis of card values, helping you build the next generation of tools for collectors, players, and sellers.

Dive into the updated **API Documentation** to see the new fields in action. We’re excited to see what you build with them!