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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds meaningful behavioral context beyond that: it lists the exact fields returned (type, title, URL, author, score, HTML-stripped body, comment count, child comment IDs up to 10, direct HN link) and notes that no auth is required. It also discloses the data source and license, which is useful for an agent deciding whether to use the data.

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 a single, information-dense paragraph that front-loads the core action and resource, then lists return fields, then covers auth and licensing. Every sentence earns its place; there is no filler or repetition of schema content.

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 single-parameter read-only lookup tool with a rich output schema, the description is complete. It covers what the tool does, what item types it handles, what fields are returned, that no auth is needed, and the data license. An agent has everything needed to select and invoke it 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?

Schema coverage is 100% and the schema already describes the id parameter well, including type, example, and exclusivity. The description reinforces the parameter's meaning by stating it works for all item types and by listing the return fields, which helps an agent understand what the ID refers to. With full schema coverage, the baseline is 3; the description adds a bit of extra context (item type coverage, return fields) but doesn't go deep into ID format edge cases.

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 ('Fetch full details') and a precise resource ('any HackerNews item by its integer ID'), then enumerates the item types it covers (stories, comments, Ask HN, Show HN, jobs, polls). This clearly distinguishes it from sibling tools like hackernews.stories.top or hackernews.user.profile, which serve different resources.

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 states the tool works for any item type and requires only an integer ID, which gives clear context for when to use it. It doesn't explicitly name alternatives or exclusion conditions, but the item-type enumeration and the sibling set (stories lists, user profile) make the usage boundary reasonably clear. A small gap: no explicit 'use this instead of X when...' guidance.

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