Who am I

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description usefully clarifies that the account is derived from the API key rather than passed in, but adds nothing about auth failure modes or rate limits — modest added value over 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?

One short sentence with zero filler, front-loading the action and the two pieces of information returned.

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?

A trivial, parameterless tool with full annotation coverage and an output schema that documents return shape, so little description is needed. What is missing is minor: whether the call fails without a valid key, and how it relates to get_usage, which also surfaces plan information.

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?

Zero parameters, so there is nothing for the description to disambiguate; baseline 4 applies. The description correctly signals that identity comes from the credential, not from inputs.

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: reveals the account the API key belongs to plus its plan. This is meaningfully distinct from all siblings, though it does not name any of them (e.g. get_usage) to reinforce the boundary between account identity and usage metrics.

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?

Usage is only implied — an agent would infer it should call this when it needs to identify the current principal or plan before other operations. There is no explicit when-to-use statement, no exclusion versus get_usage, and no note about prerequisites.

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