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

Annotations already cover read-only, idempotent, non-destructive, and open-world, so the bar is lower — and the description still adds the auth/permission model (keyless vs OAuth token), which is the main behavioral unknown for this call. Rate limits and behavior on private profiles without a token (error vs empty) are left unstated.

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?

A single compact sentence that front-loads the resource and then the auth rule. Every clause earns its place, with no filler or restatement of the title.

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?

An output schema exists, so return shape needn't be described, and the auth requirement is fully covered. The only missing piece an agent would want is the explicit hand-off to `current_user` for self-lookups.

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 only 50%, and `user_id` has no schema description at all; the description compensates by revealing that it accepts a username as well as an ID. `_apiKey` is already well documented in the schema, so no repetition is needed.

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?

Names the concrete resource (public WakaTime profile) and the identifier (user_id/username), so an agent knows exactly what it returns. It stops short of explicitly distinguishing itself from the sibling `current_user`, which is the obvious confusion point for 'your own' profile.

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?

Gives clear selection logic on the auth axis: keyless for public profiles, pass `_apiKey` for your own or private ones. It does not name `current_user` as the alternative for self-lookup, so the sibling boundary is implied rather than stated.

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