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

Annotations already declare the tool read-only, idempotent, and non-destructive, so the description doesn't need to repeat that. It adds valuable context by stating 'No auth required' and 'Data: Hacker News (CC BY 3.0)', which are behavioral and licensing facts an agent would need. This exceeds the baseline by providing additional operational transparency without contradicting the 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 three sentences, each serving a purpose: what the tool does, when to use it, and operational/licensing details. It is front-loaded with the primary action and return data, with no filler or redundancy. Every sentence earns its place.

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 tool with an output schema and read-only annotations, the description is complete: it identifies the input (username), describes the output fields, gives a use case, and notes that no auth is required. There are no gaps that would prevent an agent from selecting and invoking the tool 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?

The input schema already has 100% coverage, including the parameter's case-sensitivity and examples, so the description doesn't need to add much. The description repeats the return fields but adds no new semantic meaning for the 'username' parameter beyond what the schema provides. Baseline 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 clearly states the verb and resource ('Fetch a HackerNews user profile by username') and lists the returned fields, so its purpose is unambiguous. However, it does not differentiate from the closely related 'hnalgolia.user.profile' sibling, which could be confused with this tool. The name itself disambiguates, but the description doesn't explicitly address that potential confusion.

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 provides a clear use case ('checking contributor credibility or researching HN community members'), which gives the agent context for when to select this tool. It does not mention explicit when-not-to-use or alternatives, but the context is clear enough and no misleading guidance is given. This matches 'clear context, no exclusions'.

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