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Crypto Fear & Greed Index MCP. The Crypto Fear & Greed Index (alternative.me) — a daily 0–100 market-sentiment gauge for crypto, where 0 = Extreme Fear and 100 = Extreme Greed. Widely cited as a contrarian signal: extreme fear can mean buyers are oversold, extreme greed can mean a correction is due. Keyless, updated once per day.
Two tools with clear, descriptive names and good descriptions (both 150+ chars). Schemas present but incomplete: current_index has empty properties (no params needed, acceptable); index_history has limit param with type and description. Output schemas are NOT documented, LLMs cannot predict return structure. Error handling returns generic {error: string} without recovery guidance. No parameter validation constraints (e.g., limit bounds 1 - 365 not enforced in schema, only in code). Tool descriptions are strong (explain what, when, return value), but lack dependency hints or error recovery paths.
Get today's Crypto Fear & Greed Index — a 0–100 market-sentiment gauge for crypto (0 = Extreme Fear, 100 = Extreme Greed). Returns the current value, its classification, the date, and seconds until the next daily update. Keyless.
Get historical Crypto Fear & Greed Index values (most recent first), plus a summary (latest, average, min, max). Each entry has a date, the 0–100 value, and its classification. Keyless.
Output schemas not documented. LLMs cannot predict return structure (e.g., does current_index return {value, classification, date, seconds_until_next_update} or a different shape?). Agents must infer from trial-and-error.
Parameter constraints not enforced in schema. index_history limit accepts 1 - 365 (enforced in code), but schema has no minValue/maxValue. LLMs may pass invalid values; validation happens at runtime, not schema-time.
Error responses lack recovery guidance. callTool catches all errors and returns {error: string}. LLMs receive no hint whether to retry, ask user, or abandon. E.g., 'alternative.me: 503 Service Unavailable' gives no next step.
No tool annotations (readOnlyHint, idempotentHint). Both tools are read-only and idempotent, but schema does not declare this. Agents cannot infer safety properties.
| Scored | Grade | Overall | Spec posture | Rubric |
|---|---|---|---|---|
| 2026-09-23 | D | 57 | 2026-07-28+ | v2 |
index_history returns raw history array without pagination support. If limit=365 returns 365 items, response bloats context. No offset/cursor or result count guidance.