whoami

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

With no annotations, the description carries the full burden of behavioral disclosure. It explicitly states the operation is 'cheap' and has 'no side-effects,' and it describes what is returned. It does not cover error behavior for an invalid token, but for a simple read-only identity check the disclosure is adequate.

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 filler: the primary action and return fields come first, followed by the behavioral caveat and recommended usage. Every clause earns its place.

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 zero-parameter, no-output-schema tool, the description is complete: it identifies the resource, lists the returned fields, affirms safety, and gives a concrete usage recommendation. Nothing needed to invoke or interpret the call is missing.

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 input schema has zero parameters and 100% coverage, so the baseline is 4. There are no parameter semantics to explain, and the description does not need to add anything beyond what the schema already trivially communicates.

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 states a clear verb and resource: it confirms the configured API token and returns the principal user with a specific list of fields. It is clearly distinguished from sibling tools like list_products or post_ask, which operate on marketplace entities rather than identity.

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 explicit context for when to call it: 'Call once on startup to cache the user id.' It does not name alternatives or exclusions, but given the tool's unique identity-checking role among unrelated siblings, no alternative is genuinely needed.

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