The Safecast MCP server demonstrates solid engineering with clear, action-verb naming and well-structured schemas across all 8 tools. All tools are explicitly registered with type-safe parameter definitions and descriptions. Descriptions are substantive (ranging 40 - 160 characters per tool) and explain purpose and context. Input schemas use proper JSON Schema with typed constraints (min/max for numbers, enums for topic selection, latitude/longitude bounds). However, there are gaps in output schema documentation, while code shows structured responses being built, the MCP tool definitions do not formally document return types or structures. Error handling is adequate but not guided (errors return bare messages without recovery suggestions). The server demonstrates strong adherence to composition patterns: each tool has a single responsibility, all use READ_ONLY annotations appropriately, and parameter naming is consistent (lat/lon, device_id, track_id, limit). Pagination is present (limit, default, max constraints) but not uniformly documented. No sensitive data exposure detected. Overall, this is a B+/A− tier server with definition quality exceeding the median community server; minor gaps prevent a higher score.

• Add formal output schemas to each tool definition. Document the structure of results returned: for query_radiation, specify that response contains { measurements: [{id, value, unit, location: {lat, lon}, captured_at, detector}], count, source }, with field types and presence rules.
• Enhance error messages with recovery steps. Change 'device_id must be a number: xyz' to 'device_id must be a numeric string (got: xyz). Call list_devices() to discover valid device IDs, or search_measurements() to explore available data.' This guides agent retry logic.
• Standardize pagination. All list/search tools should return { results: [...], count, total_available, next_cursor } structure, with consistent 'limit' and optional 'cursor' parameters. Document whether cursors are opaque tokens or numeric offsets.
• Document parameter dependencies explicitly. In list_tracks, update month description to: 'Filter by month (1 - 12). Required: year parameter must also be specified. Omit to list all months for the given year.' In get_track, clarify: 'from and to are optional marker ID boundaries; if both omitted, returns full track in reverse chronological order.'
• Add per-enum-value descriptions. Extend radiation_info schema to { topic: { enum: ['units', ...], description: 'Reference topic. units: SI and legacy radiation units (Bq, Ci, Sv, Rem); dose_rates: background and dangerous exposure rates; safety_levels: occupational and public exposure limits; detectors: bGeigie and sensor types; background_levels: worldwide baselines; isotopes: common isotopes detected.' } }