Two tools with clear names and reasonable descriptions, but significant gaps in schema completeness and parameter documentation. The 'evaluate' tool has a well-structured input schema with type and description for both parameters, but the 'clear' tool has no input parameters documented. Output schemas are not formally documented, responses are free-form strings rather than structured objects. Error handling exists in the code but is not reflected in tool descriptions. No tool annotations (readOnlyHint/destructiveHint) despite clear semantic differences between the tools.

• Add tool annotations: mark 'evaluate' with readOnlyHint=true; mark 'clear' with destructiveHint=true. This signals to LLMs which tools are safe to retry and which have side effects.
• Return structured objects instead of strings. E.g., evaluate() should return {"result": 7, "stack": [7], "error": null} instead of 'Result: 7'. This enables reliable parsing and chaining.
• Document error cases in the 'evaluate' description: 'Returns error if expression is invalid, operands are insufficient, or division by zero occurs. Error message includes the specific problem.'
• Refactor session state: either pass stack as a parameter to each tool, or document that this server maintains per-client session state and requires Mcp-Session-Id (deprecated pattern, migrate to stateless design).
• Add output schema documentation to both tools, specifying the structure of success and error responses.