Single tool with critical gaps. Tool 'generate_doc' has a basic description (54 chars, within bounds) and a single parameter with type and description. However, schema is minimal, output structure is completely undocumented, and error handling is generic. The tool calls external APIs (reading FORMAT_PATH environment file) but has no documented output schema, pagination guidance, or structured response definition. Baselines from the rubric show A+ tools have 100% documented return types and average description length of 194 chars; this tool at 54 chars is brief. Parameter 'code' is appropriately named and described but the tool lacks guidance on what structured output to expect. The implementation shows generic error handling with McpError but no recovery guidance for the LLM. Instructions in ServerHandler are placeholder text copied from a counter example, not relevant to documentation generation.

• Add detailed output schema documentation: Define structured response fields (e.g., generated_documentation: string, format_name: string, function_signature: string). Return JSON with typed fields, not plain text.
• Expand tool description to 150-250 characters. Include: WHAT (generates Rust doc comments), WHEN (when you need to document a function), WHAT it needs (function code in valid Rust syntax), WHAT it returns (formatted documentation matching FORMAT_PATH template).
• Add input parameter constraints: Describe expected Rust syntax, minimum code length, required function signature components. Example: 'The Rust function code to document. Must be valid Rust syntax (fn keyword, parameters, return type). Minimum 20 chars, max 5000 chars.'
• Implement actionable error messages with recovery paths. Examples: If FORMAT_PATH missing → 'Format file not found. Set FORMAT_PATH environment variable. Available formats: [list]. See documentation for format template examples.'; If code is invalid → 'Invalid Rust syntax detected in code parameter. Ensure function includes: fn keyword, parameter list, return type.'
• Replace placeholder ServerHandler instructions with accurate description: 'This MCP server generates documentation comments for Rust functions using a customizable format template. Provide function code; server returns formatted documentation ready to insert into source.'
• Document whether tool supports batching (multiple functions at once) or single-function processing, and clarify idempotence (same code input always produces same output).

Inferred effective spec: <=2025-11-25.

• Relies on Logging (deprecated) - log to stderr or use OpenTelemetry