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

Annotations already declare readOnly, idempotent, and non-destructive behavior. The description adds useful behavioral context beyond that: it returns a specific payload shape, includes only the top 5 comments, requires no auth, and covers multiple HackerNews item types. 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?

Three short sentences, front-loaded with the core action and resource. Every clause contributes: endpoint, return fields, supported types, auth requirement, and data source. No filler 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?

With a single well-documented parameter, strong annotations, and an output schema present, the description fully satisfies what an agent needs to select and invoke this tool correctly. It even adds the no-auth and supported-item-type context that the schema does not convey.

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 full coverage for the single parameter: it specifies integer type, positive range, supported item types, and an example. The description's 'integer ID' phrase adds little beyond what the schema already provides, so the 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 opens with a specific verb and resource: 'Fetch full details for any HackerNews item by integer ID using the Algolia API.' It also names the returned fields and supported item types, so an agent can immediately distinguish this detail-fetch operation from search- or user-oriented siblings.

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 intended use is clear: call this when you have an item ID and want full details including top comments. It does not explicitly name alternative tools like hnalgolia.search.comments or hackernews.stories.top, but the scope and 'by ID' framing make the appropriate context obvious.

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