bell-mcp defines 2 tools with clear, action-verb names (ring_bell, list_bells) and reasonable descriptions (100 - 150 chars). Both tools have documented input schemas with type info and parameter descriptions. However, output schemas are not formally documented, responses are plain strings rather than structured objects. Parameter descriptions are adequate but lack explicit constraints (e.g., sound enum values are listed in prose, not as a formal enum constraint). Error handling is minimal: ring_bell validates the sound parameter and raises ValueError with a recovery hint, but list_bells has no error path. No tool annotations (readOnlyHint, idempotentHint) are present. Overall, the server is above-average for a small utility tool but lacks the polish of production-grade servers.

• Convert string responses to structured JSON objects: ring_bell should return {"status": "success", "sound": "ding", "title": "Ding", "description": "...", "message": "..."} instead of a plain string. This enables LLMs to extract and chain data.
• Add JSON Schema enum constraint to the 'sound' parameter: {"type": "string", "enum": ["beep", "ding", "ding-ding", "warning"], "description": "..."} instead of listing values in prose.
• Annotate tools with readOnlyHint and idempotentHint. Add to ring_bell: {"readOnlyHint": false, "idempotentHint": true}. Add to list_bells: {"readOnlyHint": true}.
• Wrap error responses in a structured format: {"status": "error", "code": "invalid_sound", "message": "Unknown sound 'xyz'. Choose one of: beep, ding, ding-ding, warning.", "recovery": "Call list_bells() to see available options."} instead of raising raw ValueError.
• Consider HTTP+SSE or Streamable HTTP transport to enable remote deployment and hosted client integration. STDIO limits the server to local CLI use.