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

The readOnlyHint annotation already covers the main safety trait, and the description adds useful context by noting the call is free and listing response contents such as server version and capabilities. However, it does not disclose potential authentication requirements, error conditions, or rate limits, which would be valuable given there is no output schema. The description adds some context but not rich behavioral detail beyond the annotation.

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 a single, information-dense sentence that front-loads the primary purpose and appends the cost note at the end. Every word contributes meaning, with no repetition of schema content or filler. This is exemplary conciseness for a simple 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?

For a parameterless, read-only account-query tool, the description gives a complete high-level inventory of the response: identity, plan, credits including daily cap, storage usage/quota, and server version/capabilities. It does not specify data types or units, but the lack of an output schema makes some ambiguity unavoidable. Overall, an agent knows exactly what information it can obtain from this tool.

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 accepts zero parameters and the input schema is an empty object, so there is nothing for the description to explain. Per the zero-parameter baseline, the description needs no additional parameter documentation. There is no gap in this dimension.

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 identifies the tool as an account/status query, enumerating exactly what it returns: identity, plan, credits (balance and daily cap), storage used/quota, and server version/capabilities. It is instantly distinguishable from all sibling tools, none of which provide this account-level information. Despite not using an explicit verb, 'whoami' is a standard convention and the description is unambiguous.

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 provides clear context: use this tool when you need the current user's identity, plan, credits, storage, or server capabilities. No sibling tool overlaps with this functionality, so there are no alternatives to exclude. The absence of an explicit 'when to use' statement is acceptable because the tool's purpose is self-evident and uniquely scoped.

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