mcp-server

Fear & Greed index

fear_greed_index

Read-onlyIdempotent

Current Fear & Greed index value and historical trend.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "fear_greed_index"
  }
}

Input Schema

Name	Required	Description	Default
No arguments

Output Schema

Name	Required	Description
`value`	Yes	Current index, 0 (extreme fear) to 100 (extreme greed)
`history`	No	Recent trend of the index
`updatedAt`	No
`classification`	Yes	Label, e.g. `Greed`, `Neutral`, `Extreme Fear`

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedMay 21, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "properties": {
+    "classification": {
+      "description": "Label, e.g. `Greed`, `Neutral`, `Extreme Fear`",
+      "type": "string"
+    },
+    "history": {
+      "description": "Recent trend of the index",
+      "items": {
+        "additionalProperties": true,
+        "properties": {
+          "timestamp": {
+            "description": "ISO-8601 timestamp of the data point",
+            "type": "string"
+          },
+          "value": {
+            "description": "The recorded numeric value",
+            "type": "number"
+          }
+        },
+        "required": [
+          "timestamp",
+          "value"
+        ],
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "updatedAt": {
+      "type": "string"
+    },
+    "value": {
+      "description": "Current index, 0 (extreme fear) to 100 (extreme greed)",
+      "maximum": 100,
+      "minimum": 0,
+      "type": "integer"
+    }
+  },
+  "required": [
+    "value",
+    "classification"
+  ],
+  "type": "object"
+}

First observedMay 20, 2026

TDQS

A3.9/5.0

Behavior3/5

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint, so the description's mention of 'current' and 'historical' adds limited value. It does not detail behaviors like data source or update frequency, which would be helpful beyond annotations.

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 a single concise sentence, appropriately sized for a simple tool. It front-loads the key information, though it could benefit from a minor structural improvement (e.g., separating current and historical aspects). Still, it is efficient.

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

Completeness4/5

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

Given the tool is parameterless, has comprehensive annotations, and an output schema exists to detail the return value, the description is nearly complete. It covers the essential purpose. A slight gap is the lack of mention of data resolution or period, but this is minor.

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

Parameters4/5

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

The tool has zero parameters and schema description coverage is 100% (trivially). Per guidelines, baseline is 4 for 0 params. The description adds no parameter information, but none 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 clearly states the tool provides the 'current value and historical trend' of the Fear & Greed index, which is a specific verb+resource combination. It distinguishes itself from siblings like 'market_summary' and 'get_price' by focusing on a distinct market sentiment metric.

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

Usage Guidelines3/5

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

The description implies the tool is for general market sentiment, and siblings suggest alternatives for specific coin data, but no explicit when-to-use or when-not-to-use guidance is provided. The agent must infer context from sibling names.

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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