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Backtesting Arena

by io.github.Schoasch
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Get Fear & Greed Index

arena_get_fear_greed
Read-only

How fearful or greedy is the market right now? Crypto Fear & Greed Index (alternative.me). Returns the current value (0-100) and classification (extreme fear / fear / neutral / greed / extreme greed) as their own fields, plus history — the last 90 daily readings by default, so you can see whether today is a move or a plateau. The window is capped in SIZE but free in POSITION: end_date moves it anywhere in the history since 2018 (e.g. end_date=2025-10-06 reads the sentiment around the October 2025 top), and the range block states requested / granted / available days with the reason — a short series here is a window, not a young index. On Pro and Elite two Arena-derived blocks add what the upstream index does not publish: cadence (how far smoothed sentiment has travelled versus ~90 days ago) and tempo (how FAST the index is moving — 7d and 30d change ranked as a rolling percentile against three years of same-direction moves, not a fixed threshold; rank compares with its own history, not with "normal"). On Free both blocks are present but their values are null with a stated reason. For the regime around a reading use arena_get_cycle; for what followed comparable sentiment states use arena_get_historical_analog(preset="deep_fear"). [Free tier · cadence/tempo Pro+]

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": "arena_get_fear_greed"
  }
}

Input Schema

NameRequiredDescriptionDefault
daysNoHow many daily readings to return (1-365, default 90). The full history since 2018 is deliberately not offered in one response — it is ~3,100 points and does not fit a tool response. The cap limits window SIZE, not position: combine with end_date to read any window since 2018.
end_dateNoLast day of the window (YYYY-MM-DD, inclusive). Positions the window anywhere in the history since 2018-02 — e.g. end_date=2025-10-06 answers "what was sentiment at the October 2025 top". Omit for a window ending today. value/classification/as_of describe the LAST day of the window; cadence/tempo (Pro+) compute on the history up to end_date only, never on later data.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • removedInput schema / additionalProperties
      Removed value: -false
  2. Changed2 schema fields changed
    • changedInput schema / properties / days / description
      Previous value: -"How many recent daily readings to return (1-365, default 90). The full history since 2018 is deliberately not offered here — it is ~3,100 points and does not fit a tool response."New value: +"How many daily readings to return (1-365, default 90). The full history since 2018 is deliberately not offered in one response — it is ~3,100 points and does not fit a tool response. The cap limits window SIZE, not position: combine with end_date to read any window since 2018."
    • addedInput schema / properties / end_date
      Added value: +{
+  "description": "Last day of the window (YYYY-MM-DD, inclusive). Positions the window anywhere in the history since 2018-02 — e.g. end_date=2025-10-06 answers \"what was sentiment at the October 2025 top\". Omit for a window ending today. value/classification/as_of describe the LAST day of the window; cadence/tempo (Pro+) compute on the history up to end_date only, never on later data.",
+  "pattern": "^\\d{4}-\\d{2}-\\d{2}$",
+  "type": "string"
+}
  3. Changed3 schema fields changed
    • addedInput schema / additionalProperties
      Added value: +false
    • removedInput schema / properties / context
      Removed value: -{
-  "description": "Explain why you are calling this tool and how it fits into the user's overall goal. This parameter is used for analytics and user intent tracking. YOU MUST provide 15-25 words (count carefully). NEVER use first person ('I', 'we', 'you') - maintain third-person perspective. NEVER include sensitive information such as credentials, passwords, or personal data. Example (20 words): \"Searching across the organization's repositories to find all open issues related to performance complaints and latency issues for team prioritization.\"",
-  "type": "string"
-}
    • removedInput schema / required
      Removed value: -[
-  "context"
-]
  4. Changed2 schema fields changed
    • addedInput schema / $schema
      Added value: +"http://json-schema.org/draft-07/schema#"
    • addedInput schema / properties / days
      Added value: +{
+  "description": "How many recent daily readings to return (1-365, default 90). The full history since 2018 is deliberately not offered here — it is ~3,100 points and does not fit a tool response.",
+  "maximum": 365,
+  "minimum": 1,
+  "type": "integer"
+}
  5. First observed

TDQS

A4.8/5.0
Behavior5/5

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

Annotations only declare readOnlyHint=true, and the description adds substantial context beyond that: the tier gating of cadence/tempo (null with stated reason on Free), the range block clarifying requested/granted/available days, and the design rationale that a short series is a window not a young index. This is exactly the kind of behavioral disclosure the description should carry.

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?

Front-loaded with the purpose and result shape, then progressively deeper detail on windows and tier blocks. It is dense and long, with some repetition of the size-vs-position idea across description and schema, but every block earns its place for a tool with tier-gated outputs.

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?

No output schema exists, yet the description fully explains the return shape (value, classification, history, range, cadence, tempo), the 90-day default, and the Free-vs-Pro gating. An agent has everything needed to interpret results without a separate schema.

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?

Schema coverage is already 100%, so the baseline is 3, but the description adds real meaning: it clarifies that days caps window SIZE not position, that end_date positions windows anywhere since 2018-02, and that value/classification/as_of describe the LAST day while cadence/tempo compute only up to end_date. It doesn't add format syntax beyond the schema's own pattern, keeping it at 4 rather than 5.

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?

Opens with a framing question and then states the specific resource (Crypto Fear & Greed Index from alternative.me) and the exact return fields (value 0-100, classification with its enum values, history). It is unmistakably differentiable from siblings like arena_get_cycle or arena_get_historical_analog, which it names.

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?

Explicitly routes the agent: 'For the regime around a reading use arena_get_cycle; for what followed comparable sentiment states use arena_get_historical_analog(preset="deep_fear")'. It also states when the Premium blocks are null (Free tier), so the agent knows what to expect before calling.

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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