Read the account behind the key

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

Annotations already declare readOnlyHint=true and openWorldHint=true, which cover the safety and dynamic nature of the tool. The description adds context about the type of data returned (plan, addons, scopes, prompt count) but does not disclose any additional behavioral traits such as error conditions, rate limits, or response format specifics. With annotations carrying the safety profile, the description adds limited extra behavioral transparency, warranting a 3.

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?

The description is two sentences with no fluff. The first sentence front-loads the core resource and the specific data points returned, and the second sentence gives practical usage scenarios. Every word earns its place, and it is perfectly scoped for a zero-parameter read-only tool.

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 there is no output schema and the tool is simple (no params), the description must convey what the agent can expect. It lists the categories of information (owner, plan, addons, scopes, prompt count) and when to use it, which is largely complete. However, it does not specify the exact field names or structure of the response, nor any error behavior for invalid keys. Still, for a tool this simple, it is sufficiently complete, so a 4 is fair.

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 has zero parameters, and the schema description coverage is 100% (vacuously). The description doesn't need to explain parameters, and it does not add any parameter semantics beyond what's relevant (none). Per the rubric, 0 params gives a baseline of 4, and the description effectively compensates by explaining what the tool returns, though that's more about output than parameter meaning.

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 clearly states the tool's purpose: it returns account details tied to the configured API key, including owner, plan, addons, scopes, and prompt count. It also gives concrete use cases ('diagnose a key', 'check whether a plan covers a feature'), which differentiates it from sibling tools that focus on projects, prompts, or visibility data.

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 tells when to use the tool ('Call this to diagnose a key or to check whether a plan covers a feature before promising it'). It does not name specific alternatives or when-not-to-use, but the context makes it clear this is for account-level diagnostics rather than project/prompt operations. It lacks explicit exclusions, so a 4 is appropriate.

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