whoami

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

With no annotations, the description carries the behavioral disclosure burden. It explains that the tool reveals the server-side user, whether expenses are scoped, and that the likely cause of invisibility is an unauthenticated request landing in the shared local bucket. This adds meaningful diagnostic context beyond the tool name.

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 first sentence is a crisp summary, and the second sentence earns its place by explaining practical value. The wording is slightly discursive with the quoted diagnostic scenario, but overall it is compact and front-loaded.

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 simple zero-parameter diagnostic tool with an output schema, the description covers purpose, usage rationale, and a common failure context. It does not explicitly state that the tool is read-only or side-effect-free, but the name and description strongly imply a safe diagnostic operation.

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 input schema is empty, so there are no parameter semantics to clarify. The baseline for a zero-parameter tool is 4, and the description appropriately does not invent parameter guidance.

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 opens with a specific verb and resource: 'Report which user the server sees, and whether expenses are scoped.' This clearly distinguishes whoami from the expense-management siblings by framing it as a diagnostic identity/scoping tool rather than a data operation.

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 gives a concrete use case: answering 'why can't I see my expenses?' in one call, and advises keeping it permanently rather than as a one-off diagnostic. It does not explicitly contrast against sibling tools or state when not to use it, but the usage context is clear.

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