Crystals MCP Server by RoxyAPI

Daily crystal - Crystal of the day API

post_crystals_daily

Read-only

Get the crystal of the day as a discovery teaser. Returns a deterministic crystal based on the current date (or a provided seed date), ensuring all users see the same crystal for any given day. Use the /crystals/{id} detail endpoint for complete spiritual, emotional, and physical healing properties. Perfect for daily guidance features, push notifications, wellness app widgets, and crystal journal integrations.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`date`	No	Date for the reading in YYYY-MM-DD format. Defaults to today (UTC). Useful for viewing past daily readings or pre-generating future ones.
`lang`	No	Response language (BCP 47). Supported: en, tr, de, es, hi, pt, fr, ru, zh-Hans, zh-Hant. Defaults to en. Coverage varies by domain, and a field with no translation in the requested language returns English.	en
`seed`	No	Optional seed for reproducible readings. Same seed + same date = same crystal every time. Pass any unique identifier (userId, email hash, session token). Omit for anonymous daily readings.
`compact`	No	Set true for the same data in a compact shape: arrays of same-shaped objects arrive columnar as {"__cols":[names],"__rows":[[values]]}. Lossless, typically 40 to 52 percent fewer tokens.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`id`	Yes
`date`	Yes
`name`	Yes
`seed`	Yes
`chakras`	Yes
`imageUrl`	Yes
`affirmation`	Yes
`description`	Yes
`zodiacSigns`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedSep 20, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "affirmation": {
+      "type": "string"
+    },
+    "chakras": {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "date": {
+      "type": "string"
+    },
+    "description": {
+      "type": "string"
+    },
+    "id": {
+      "type": "string"
+    },
+    "imageUrl": {
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "name": {
+      "type": "string"
+    },
+    "seed": {
+      "type": "string"
+    },
+    "zodiacSigns": {
+      "items": {
+        "type": "string"
+      },
+      "type": [
+        "array",
+        "null"
+      ]
+    }
+  },
+  "required": [
+    "date",
+    "seed",
+    "name",
+    "id",
+    "imageUrl",
+    "description",
+    "chakras",
+    "zodiacSigns",
+    "affirmation"
+  ],
+  "type": "object"
+}

Changed2 schema fields changedAug 25, 2026

changedInput schema / properties / lang / description

Previous value: -"Response language (ISO 639-1). Supported: en, tr, de, es, hi, pt, fr, ru. Defaults to en. Languages without translations yet return English."New value: +"Response language (BCP 47). Supported: en, tr, de, es, hi, pt, fr, ru, zh-Hans, zh-Hant. Defaults to en. Coverage varies by domain, and a field with no translation in the requested language returns English."

changedInput schema / properties / lang / enum

Previous value: -[
-  "en",
-  "tr",
-  "de",
-  "es",
-  "hi",
-  "pt",
-  "fr",
-  "ru"
-]New value: +[
+  "en",
+  "tr",
+  "de",
+  "es",
+  "hi",
+  "pt",
+  "fr",
+  "ru",
+  "zh-Hans",
+  "zh-Hant"
+]

Changed2 schema fields changedAug 17, 2026

addedInput schema / examples
```
Added value: +[
+  {}
+]
```

changedInput schema / properties / compact / description

Previous value: -"Set true to receive the exact same data in a token-optimized shape that is cheaper for you to read: whitespace is stripped and every array of same-shaped objects is encoded columnar as {\"__cols\":[field names],\"__rows\":[[values]]}, so each field name is sent once instead of once per row. Fully lossless (no field or value is dropped or changed) and typically 40 to 52 percent fewer tokens on large results. Prefer true whenever token or inference cost matters. Default false returns standard indented JSON."New value: +"Set true for the same data in a compact shape: arrays of same-shaped objects arrive columnar as {\"__cols\":[names],\"__rows\":[[values]]}. Lossless, typically 40 to 52 percent fewer tokens."

Changed1 schema field changedJul 22, 2026

changedInput schema / properties / compact / description

Previous value: -"Return the same data in a token-optimized compact shape (minified, with same-shaped arrays encoded columnar) to reduce LLM token cost. Lossless: no fields are dropped. Default false."New value: +"Set true to receive the exact same data in a token-optimized shape that is cheaper for you to read: whitespace is stripped and every array of same-shaped objects is encoded columnar as {\"__cols\":[field names],\"__rows\":[[values]]}, so each field name is sent once instead of once per row. Fully lossless (no field or value is dropped or changed) and typically 40 to 52 percent fewer tokens on large results. Prefer true whenever token or inference cost matters. Default false returns standard indented JSON."

Changed1 schema field changedJul 22, 2026

addedInput schema / properties / compact

Added value: +{
+  "default": false,
+  "description": "Return the same data in a token-optimized compact shape (minified, with same-shaped arrays encoded columnar) to reduce LLM token cost. Lossless: no fields are dropped. Default false.",
+  "type": "boolean"
+}

First observedJul 8, 2026

TDQS

A4.4/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already mark the tool as read-only and non-destructive. The description adds valuable behavioral context: deterministic selection based on date, consistency across all users for the same day, and the 'discovery teaser' nature. The phrase 'provided seed date' is slightly imprecise because the schema separates date from seed, but the core behavior is clearly disclosed.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is compact and front-loaded: the first sentence states the tool's purpose, the second explains determinism, and the remaining sentences give the alternative and use cases. It earns its length, though the use-case list is slightly expansive and 'seed date' could be worded more precisely.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a simple, read-only, fully-optional-parameter tool with an output schema present, the description covers everything an agent needs: what it returns, how determinism works, when to use it, and where to go for richer data. The annotations handle safety expectations, and the schema handles parameter details.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema already documents date, lang, seed, and compact in detail. The description adds only the general determinism concept and does not provide additional parameter-level semantics. Baseline 3 is appropriate since no compensation is needed.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb and resource ('Get the crystal of the day') and immediately clarifies its deterministic daily nature. It also differentiates from the more detailed crystals endpoint by labeling this a 'discovery teaser' and pointing to /crystals/{id} for full properties. This is enough for an agent to distinguish it from sibling tools like get_crystals_random or get_crystals_id.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description gives explicit use cases ('daily guidance features, push notifications, wellness app widgets, and crystal journal integrations') and an explicit alternative: 'Use the /crystals/{id} detail endpoint for complete spiritual, emotional, and physical healing properties.' This tells an agent both when to use this tool and when to choose the detail endpoint instead.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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