Katzilla MCP

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already provide readOnlyHint=true, destructiveHint=false, idempotentHint=true, and openWorldHint=true, indicating safe, repeatable operations. The description adds valuable context beyond this: it specifies that the service is 'Free to use' and 'updates daily', describes the return format ('Katzilla envelope { data, quality, citation }'), and explains quality metrics ('freshness/uptime/confidence') and citation details, which are not covered by annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is front-loaded with the core purpose in the first sentence, followed by additional details in a structured manner. Every sentence adds value: service verification, source information, return format, and quality explanation, with no wasted words or redundancy.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's moderate complexity, rich annotations, and the presence of an output schema (implied by 'Returns the Katzilla envelope'), the description is complete. It covers purpose, usage context, behavioral details, and output structure, leaving no significant gaps for an AI agent to understand and invoke the tool correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, with clear descriptions for both parameters ('data' and 'size'). The description adds minimal semantic value beyond the schema, only implying that 'data' can be 'any text or URL', which is already covered. With high schema coverage, the baseline score of 3 is appropriate as the schema does most of the work.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's purpose with specific verbs ('Generate a QR code image URL') and resources ('for any text or URL'), and it distinguishes itself from siblings by focusing on QR code generation, which is unique among the listed utilities tools like fetch-url, rdap-whois, unit-conversion, and url-shortener.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides clear context for usage ('Generate a QR code image URL for any text or URL') and mentions the service source ('goQR.me'), but it does not explicitly state when not to use this tool or name specific alternatives among siblings, such as url-shortener for URL handling, which could be relevant.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.