CryptoSignals402 shows mixed quality. All 9 tools have explicit registrations with descriptions and input schemas in mcp_server.py, which is positive. However, several critical issues undermine production readiness: (1) Most tools have NO parameters despite complex operations (get_funding_all, get_divergence, get_opportunities, get_bittensor_subnets, get_xrpl_pools accept empty objects), which violates the principle that parameters control behavior and guide LLM reasoning. (2) Parameter descriptions are minimal or missing constraint details (get_coin_data.hours lacks minimum/maximum constraints despite range claim '1-168'). (3) Output schemas are completely undocumented, no return type specifications visible in the tool registry, forcing LLMs to call blindly without knowing what data structure to expect. (4) Error handling is basic (generic 'error' field in responses, some context for x402 payment failures) but lacks recovery guidance for common failure modes. (5) No tool annotations (readOnlyHint, destructiveHint, idempotentHint), despite tools performing state-modifying payment transactions. Tool names follow verb_noun convention well (all 'get_*'), descriptions are reasonably detailed (120-200 chars, within production range p10=34, p90=392), and the free/paid segmentation is clear.

• Add explicit output schema documentation for every tool. Define the response structure (fields, types, nested objects) in the tool registry or OpenAPI spec. Example for get_status: 'Returns {health: string, coins_tracked: int, exchanges: int, history_depth_days: int, last_update: ISO8601}'. This enables LLMs to plan downstream composition.
• Add missing parameters to zero-parameter tools. Example: get_funding_all should accept limit (default 50, max 229), offset/cursor (for pagination), and optional filters (exchange: enum[Hyperliquid|Binance|Bybit], min_apr: float, risk_level: enum[LOW|MEDIUM|HIGH]). Even if the backend serves all data, expose pagination and filtering so LLMs can scope requests.
• Formalize parameter constraints in JSON Schema using minimum, maximum, enum, and pattern fields, not just descriptions. For get_coin_data, add: 'hours': {type: 'integer', minimum: 1, maximum: 168, default: 24}. This lets LLMs validate before calling and reject absurd values early.
• Add tool annotations to signal operational semantics. Mark all 'get_*' tools with readOnlyHint: true. Mark paid tools (those with 'Costs $0.01') with idempotentHint: false if payments are non-retryable, or include a note: 'Idempotent: x402 payments are deduplicated by request hash.' This prevents retry-induced double charges.
• Enhance error handling to include recovery hints. Instead of return {'error': 'HTTP 502: Bad Gateway'}, return {'error': 'API unreachable', 'retryable': true, 'guidance': 'Wait 30s and retry, or call get_status() to check API health'}. For 402 errors, the current hint is good, keep it for all paid tools.