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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds meaningful non-annotation context: the result is scoped to the API key's owner and the exact set of returned fields (including last heartbeat time, which implies a live/latest-state read). It does not discuss rate limits or invalid-key behavior, but for a simple authenticated GET that is a minor omission.

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?

One dense sentence plus the endpoint reference, with the resource identity front-loaded and the field list immediately after. No filler, no restatement of the title or annotations, and every clause carries information.

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?

There is no output schema, so the description carries the return-value burden itself – and it does so by enumerating the fields, which is exactly what an agent needs before deciding to call it. What is missing is only peripheral: no note on authentication failure (invalid/expired key) or caching/rate-limit behavior. For a zero-parameter read bounded by explicit safety annotations, this is nearly complete.

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 tool takes zero parameters, so the baseline is 4 per the rubric. The description correctly offers no parameter guidance because there is nothing to parameterize; all of its detail goes to the result shape instead.

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 names a specific resource ('The WakaTime user this key belongs to') and enumerates the exact fields returned (id, username, display name, email, timezone, plan, last plugin/project/branch, last heartbeat time). It also pins the underlying endpoint, GET /users/current, so there is no ambiguity about what is retrieved. No sibling tool does anything similar – the rest are stats/heartbeat/commit/org aggregations – so it is easy to route to.

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 phrase 'this key belongs to' implies the tool is for resolving the authenticated user's identity, and with zero parameters and a single obvious purpose, alternatives are effectively nil. However, the description never states when to reach for this tool (e.g., 'use to resolve the API key's owner before calling user-scoped endpoints') or any exclusions. Usage is inferable rather than stated.

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