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

Annotations already cover read-only and idempotent behavior, so the bar is lower. The description adds valuable behavioral context: matching on code, aliases, or category; the ability to list all codes when query is omitted; and the nature of output (explanation of meaning, severity, actions). These are not redundant with annotations and enhance transparency.

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?

Three sentences, front-loaded with purpose, then usage details, then context. No fluff, every sentence contributes value. Efficient and well-structured.

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?

For a simple lookup tool with one optional parameter, an output schema, and safe annotations, the description covers all essential aspects: what it does, how to invoke it, what to expect, and when to use it. No gaps identified.

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% and already explains the query parameter (code, alias, or category, omittable). The description adds extra clarity by emphasizing aliases and categories and reinforcing the listing behavior when query is omitted. This is a minor enhancement over the schema, so a 4 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?

States exactly what the tool does: 'Explain domain EPP status codes' with detail on what aspects it covers (meaning, why set, severity, holder actions). Clearly distinguishes from siblings like whois by positioning itself as an interpretation layer for the status field returned by whois. The description is specific and actionable.

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?

Provides explicit when-to-use guidance: 'Use this to interpret the status field returned by whois instead of relying on recall.' Also clarifies the invocation pattern for both query and no-query cases. Does not explicitly state when not to use it, but the context is clear enough for an agent to decide.

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