Crypto Fear & Greed Index: current and previous value plus classification (Extreme Fear to Extreme Greed), with recent history. Best used as a contrarian sentiment signal, not on its own.
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
| Name | Required | Description | Default |
|---|---|---|---|
| value | Yes | 0-100. Low is fear, high is greed. | |
| history | Yes | ||
| previousValue | No | ||
| classification | Yes | ||
| previousClassification | No |
Changes observed during successful MCP inspections.
Output schema / (root)Previous value: -nullNew value: +{
+ "properties": {
+ "classification": {
+ "type": "string"
+ },
+ "history": {
+ "items": {
+ "properties": {
+ "time": {
+ "type": "number"
+ },
+ "value": {
+ "type": "number"
+ }
+ },
+ "required": [
+ "time",
+ "value"
+ ],
+ "type": "object"
+ },
+ "type": "array"
+ },
+ "previousClassification": {
+ "type": [
+ "string",
+ "null"
+ ]
+ },
+ "previousValue": {
+ "type": [
+ "number",
+ "null"
+ ]
+ },
+ "value": {
+ "description": "0-100. Low is fear, high is greed.",
+ "type": "number"
+ }
+ },
+ "required": [
+ "value",
+ "classification",
+ "history"
+ ],
+ "type": "object"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description clearly states the tool retrieves historical data ('recent history'), complements the readOnlyHint and idempotentHint annotations by confirming read behavior. While not strictly necessary to call out, it accurately describes the output without contradictions.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
The description is extremely concise—two sentences with no wasted words. All critical information (what, what format, when to use) is front-loaded and efficiently communicated.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
The description is complete for this tool: it describes the output (current/previous value, classification, recent history), provides usage context (contrarian sentiment signal), and clarifies limitations (not standalone). The output schema presumably documents return fields, so no additional return-value explanation is needed.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
The input schema has zero parameters, so the description correctly adds no additional parameter semantics. The baseline of 3 is appropriate since there is no parameter information to supplement.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description clearly states the tool retrieves the Crypto Fear & Greed Index, including current/previous values, classification, and recent history. It effectively distinguishes itself from sibling tools by specifying the specific index it retrieves.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The description provides clear guidance on when to use the tool ('best used as a contrarian sentiment signal') and explicitly advises against relying on it in isolation ('not on its own'). This directly helps an AI agent decide when to invoke this tool versus alternatives.
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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