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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive behavior. The description adds useful behavioral context by specifying that the result spans all languages, that each entry includes the common name, ISO language code, and full language name, and by giving a concrete example. There is no contradiction with 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 compact and front-loaded: it states the action, then the return fields, a concrete example, use cases, and source/license. Every sentence adds useful context without fluff or repetition of the title.

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 tool with a single well-documented integer parameter, a full output schema, and safety annotations covering read-only/idempotent behavior, the description is complete. It tells the agent what the tool returns, gives an example, and includes licensing context, leaving no critical gap for correct invocation.

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 the parameter description already explains aphia_id with examples. The tool description adds a concrete AphiaID example (137102) and reinforces expected output fields, but it does not materially extend the schema's parameter explanation, so the high-coverage baseline 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 opens with a specific verb and resource: 'Retrieve all registered vernacular (common) names for a marine taxon by AphiaID across all languages.' This clearly distinguishes the tool from sibling worms.species.details, worms.species.classification, and worms.species.search, which deal with other aspects of taxon data.

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 gives helpful use-case context ('multilingual species identification, biodiversity apps, and natural-history content') and the example makes the intended scenario concrete. However, it does not explicitly state when to prefer this tool over sibling tools or mention any exclusions, leaving usage guidance implied rather than explicit.

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