Katzilla MCP

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

Annotations already indicate read-only, non-destructive, idempotent, and open-world behavior. The description adds valuable context beyond this: it specifies the return format ('Katzilla envelope'), details on quality scoring ('freshness/uptime/confidence'), and citation information ('source URL, license, SHA-256 hash'). This enriches the agent's understanding of the tool's behavior without contradicting 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 efficiently structured in two sentences: the first states the purpose and key return fields, the second explains the return format and data quality. Every sentence adds value, with no redundant information, making it front-loaded and concise.

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 simplicity (one parameter, full schema coverage, annotations covering safety, and an output schema implied by the return format description), the description is complete. It covers purpose, usage context, behavioral details, and output structure, leaving no gaps for the 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?

The input schema has 100% description coverage, with the 'domain' parameter clearly documented. The description does not add any additional semantic details about parameters beyond what the schema provides (e.g., no examples of valid domains beyond 'example.com' or edge cases). Given the high schema coverage, a baseline score of 3 is appropriate.

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 explicitly states the tool's purpose: 'Look up domain registration information using the RDAP protocol (successor to WHOIS).' It specifies the verb ('look up'), resource ('domain registration information'), and protocol ('RDAP'), distinguishing it from sibling tools like 'utilities__fetch-url' or 'utilities__qr-code' that serve different purposes.

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 when to use this tool: for domain registration lookups via RDAP. It mentions the data source ('RDAP.org') and update frequency ('daily'), which helps set expectations. However, it does not explicitly state when not to use it or name alternatives (e.g., traditional WHOIS tools), keeping it from a perfect score.

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