get_user

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

Annotations only declare readOnlyHint and openWorldHint; the description adds genuinely new behavioral context the agent needs: case-sensitive usernames and the API's restriction to accounts with public activity. It does not cover failure modes for unknown or private accounts, which leaves a small gap.

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?

Front-loaded with purpose, then behavior caveats, then the routing note — good ordering, no filler. The "Returns karma, account age, bio and submission count" sentence partly duplicates the output schema, so it is not maximally lean.

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 one-parameter read-only lookup with an output schema, everything an agent needs is present: what it fetches, how usernames behave, what HN will not expose, and where to go for submissions.

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 0% (no parameter descriptions), so the description must carry the burden — and it does, flagging that usernames are case-sensitive, a real invocation constraint. It stops short of giving format examples or length/shape guidance for the single required parameter.

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?

States a specific verb and resource ("Look up a Hacker News user profile") and immediately distinguishes itself from the profile-vs-content sibling boundary. An agent can tell this apart from search_stories without inspecting either schema.

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?

Explicitly names the exclusion ("returns the profile, not the user's posts") and routes to the alternative ("use search_stories"). That is the when-to-use/when-not pattern done properly.

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