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

Annotations include readOnlyHint: true and openWorldHint: true, which already signal a safe read and dynamic data. The description adds no additional behavioral context beyond that, such as whether the item includes comments, type of item, or any rate limits. It does not contradict the annotations. Since annotations cover safety, a 3 is appropriate, but the description could add value by stating that the item may be of any type (story, comment, poll, job) and that it returns both metadata and text.

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?

Extremely concise: a single sentence, front-loaded with purpose. No fluff, but it could have been slightly more informative without being verbose. It earns a 4 for efficiency and clarity, though it misses opportunities to add value within the same brevity.

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 10 parameters (though most have generic placeholder descriptions), an output schema absent, and a description that only says 'by id', the description is incomplete for correct usage. The common pattern of pagination parameters (limit, offset, etc.) is unclear whether they apply. The description does not specify that the item can be of any HN type or that nested fields exist. Given the complexity and the lack of an output schema, more descriptive context is needed.

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 coverage is 100% - every parameter has a description in the schema. The description adds no extra parameter semantics beyond 'by id'. However, the schema already describes id, so the description adds minimal value. Many parameters (trim, limit, offset, pageSize, maxResults, max_results) are marked 'Ignored if this tool does not support it.' The description does not clarify which of these are actually used, but the schema already covers that implicitly. Baseline 3 is appropriate since the schema does the heavy lifting.

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 'Get a H hacker News item by id.' clearly states a specific verb and resource, and mentions the id parameter. It distinguishes from sibling tools like hackernews_story_get or hackernews_comment_get by the broad term 'item', but does not explicitly differentiate from those siblings. It is clear and actionable, but lacks explicit differentiation from closely related tools that also get specific HN items (stories, comments).

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?

No guidance on when to use this tool versus alternatives like hackernews_story_get or hackernews_comment_get. The description only states what it does and doesn't provide context about when to prefer this over other HN item retrieval tools, nor exclusions. The user must infer from the id type or other hints.

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