HelloMCP is a minimal example server with one tool (add). The tool has a valid description ('Add two numbers') and a properly typed input schema with integer parameters. However, parameter descriptions are entirely missing (null values in schema), violating the critical requirement that every parameter must have a description. The tool is simple and functional but lacks the documentation depth required for production use. No error handling, no output schema documentation, and no guidance on when/why to use the tool beyond the bare description.

• Add descriptions to all parameters: 'a' and 'b' should explain they are the two numbers to add, with optional range constraints (e.g., 'Integer in range -1000000 to 1000000').
• Expand tool description to 50-150 characters: 'Add two integers and return their sum. Use this for arithmetic operations. Returns the result as an integer.'
• Document the output schema explicitly: 'Returns: integer (the sum of a and b)'.
• Add input validation with actionable error messages: if inputs are not integers or exceed bounds, return 'Invalid input: a and b must be integers in range [-1000000, 1000000]'.
• Consider adding optional parameters like 'precision' or 'rounding_mode' if the tool will evolve, or keep it simple and document that it only handles exact integer addition.