Single tool with adequate schema and basic description. Tool naming is action-oriented (generate_image), input schema is complete with typed parameters and descriptions. However, output schema is not documented in the tool definition itself (only returned as a response, not declared upfront). Parameter descriptions are minimal and lack context about prerequisites, constraints, or error recovery. No error handling guidance provided. The tool performs a write operation (calls external API, writes file) but description does not explicitly state this has side effects. Missing documentation around API key injection, rate limits, and what happens on generation failures.

• Expand tool description to ~150-200 chars explaining: (1) What it does: generates images via DALL-E-3. (2) When to use it: when user asks to create, visualize, or illustrate something. (3) Mutability: writes PNG files to ~/Desktop/generated-images/. (4) Prerequisites: requires OPENAI_API_KEY environment variable. Example: 'Generate images from text prompts using DALL-E-3. Writes PNG files to ~/Desktop/generated-images/. Requires OPENAI_API_KEY env var. Returns file URI and MIME type of the generated image.'
• Add constraint documentation to parameters: 'prompt' description → 'Text description of the image (1-2000 chars, English recommended for best results).' 'imageName' description → 'Filename without extension (will be sanitized to remove invalid chars; .png added automatically; if file exists, timestamp is appended).'
• Document output schema in the inputSchema or add a separate 'outputSchema' field: {type: 'object', properties: {uri: {type: 'string', description: 'file:// URI to generated PNG'}, type: {type: 'string', enum: ['image']}, mimeType: {type: 'string', enum: ['image/png']}}, required: ['uri', 'type', 'mimeType']}
• Add error handling to CallToolRequestSchema handler. Wrap ImageGenerator.generateImage() in try-catch and return McpError with recovery guidance: 'Failed to generate image: <reason>. Ensure OPENAI_API_KEY is set and you have remaining API quota.' For file write failures: 'Failed to save image to disk: <reason>. Check ~/Desktop/generated-images/ is writable.'
• Add idempotency hint to description or annotations: 'Multiple calls with the same prompt may produce different images (DALL-E-3 output varies). To regenerate, use a different prompt or imageName to avoid file overwrites.'