Here are a few options for a WordPress post_tag description for “比特幣匯率” (Bitcoin Exchange Rate) in Traditional Chinese, ranging in detail and focus:

**Option 1 (Concise & Broad):**

> 比特幣的即時匯率和價格波動。

**(Translation: Bitcoin’s real-time exchange rate and price fluctuations.)**

* **Suitable for:** General use, simple filtering.

**Option 2 (More Detailed):**

> 關於比特幣 (Bitcoin) 兌換其他貨幣的匯率，包括實時價格、每日漲跌幅、以及影響匯率的因素。

**(Translation: Information about Bitcoin’s exchange rate against other currencies, including real-time prices, daily gains and losses, and factors that influence the exchange rate.)**

* **Suitable for:** Providing a little more context for readers interested in exchange rate information.

**Option 3 (Targeted towards News/Analysis):**

> 最新比特幣匯率新聞、分析報告、以及影響比特幣價格的趨勢與事件。

**(Translation: Latest Bitcoin exchange rate news, analysis reports, and trends and events affecting Bitcoin prices.)**

* **Suitable for:** If your posts often cover news and analysis about the Bitcoin market.

**Option 4 (Emphasizing Monitoring):**

> 監測比特幣 (Bitcoin) 匯率變化，追蹤最新價格，並了解比特幣兌美元、人民幣等其他貨幣的匯率走勢。

**(Translation: Monitor Bitcoin (Bitcoin) exchange rate changes, track the latest prices, and understand the exchange rate trends of Bitcoin against USD, RMB, and other currencies.)**

* **Suitable for:** Helping readers get insights that require observing exchange rates regularly.

**Which option should you choose?**

* **Think about the content associated with this tag:** What kind of posts will use it?
* **Consider your audience:** What are they looking for?
* **Keep it relatively short:** (WordPress will truncate it if it’s too long).

I recommend either **Option 1** (for simplicity) or **Option 2** (for a bit more context) depending on the nature of your content. You can always modify or combine elements from these suggestions to create a description that perfectly suits your needs. Also, try using the word “匯率” in other relevant posts and tags to improve your site’s SEO.