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

The description goes well beyond the readOnly/idempotent annotations by explaining critical response nuances: the difference between the API key row id and user id, the 'user' field as the entityId for stats tools, and the 'team' field as project ID. It also documents null behavior for userName, adding substantial behavioral context that the annotations do not cover.

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?

Three sentences, each serving a distinct purpose: stating the core function, indicating typical use, and disambiguating response fields. No fluff or redundancy; the length is justified by the important warnings about id semantics.

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?

Given the simple input schema and lack of output schema, the description fully compensates by specifying exactly what fields appear in the response and how to interpret them correctly. It anticipates common mistakes (confusing API key id with user id) and provides complete guidance for using the returned data with other tools like stats_fetch.

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?

There are zero parameters and the schema is empty (100% coverage trivially). The baseline for 0 params is 4, and the description does not need to add parameter information. It instead enriches understanding of output fields, which is beyond this dimension's scope but still helpful.

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 uses specific verb 'Returns information about the current API key' and clearly identifies the resource and the content (authenticated user, project/team). It distinguishes itself from all sibling tools, including ping, by focusing on authentication identity rather than connectivity or resource operations.

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 explicitly states 'Useful to verify authentication and retrieve your user ID or project ID,' providing clear context for when to call the tool. It does not name alternative tools, but there are no direct competitors among siblings, so the guidance is adequate though not exhaustive.

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