This server demonstrates solid definition quality with consistent tool naming, complete parameter schemas, and clear descriptions. All 4 tools follow verb_noun naming conventions (pushover_send_message, pushover_check_receipt, pushover_cancel_receipt, pushover_cancel_receipt_by_tag). Parameter schemas are well-structured with types and descriptions present for all inputs. However, there are gaps in output documentation (no visible return schema definitions), missing parameter constraints (enums for priority values, string length/format documentation), and incomplete error handling guidance. The server validates inputs thoroughly at runtime but does not communicate constraints clearly in parameter descriptions. Tool compositions are sound, each performs a single responsibility. No security issues detected (no secrets in parameters).

• Add explicit JSON Schema definitions for all tool outputs. Document fields like 'receipt' (string), 'status' (integer), 'errors' (array of strings), 'request' (string from send_message), and any other response fields. Include example output structures in tool descriptions.
• Convert priority from free-form number to enum in schema: {"enum": [-2, -1, 0, 1, 2]} with human-readable names in description: 'Priority level: -2 (lowest), -1 (low), 0 (normal, default), 1 (high), 2 (emergency with required retry/expire).'
• Add JSON Schema constraints for character limits on pushover_send_message: title maxLength 250, device maxLength 25, url maxLength 512, url_title maxLength 100, message maxLength 1024. Include minLength/maxLength for numeric bounds (retry minimum 30, expire max 10800, ttl positive, timestamp valid Unix epoch).
• Formalize mutually exclusive constraint: document in schema or add explicit parameter dependency rules. E.g., 'If html=true, monospace must be false.' Consider rejecting both=true with clear error: 'html and monospace cannot both be true, use one or neither.'
• Enhance error messages with recovery guidance. Examples: 'Message exceeds 1024 characters (got {actual_length}). Try splitting into multiple messages or removing formatting.' Or 'Emergency priority (priority=2) requires retry (min 30s) and expire (1-10800s). Provide both parameters.'
• Add a pushover_preview_cancellation tool that shows which notifications would be cancelled by a tag without actually cancelling them. This lets agents verify intent before executing pushover_cancel_receipt_by_tag.