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

With no annotations, the description carries the full burden. It transparently discloses the Authorization: Bearer requirement and indicates the returned data fields. For a simple read-only operation, this is adequate behavioral disclosure, though it does not mention error behavior or exact output formatting.

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 sentence that front-loads the core purpose, lists the relevant fields, and adds the auth requirement. Every word earns its place; there is no redundancy or fluff.

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 the tool's simplicity — zero parameters and no output schema — the description covers the essential information: what it returns and the required authorization. The vague term 'stats' is a slight gap, but overall the description is sufficiently complete for an agent to call and interpret the result.

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 coverage is trivially 100%. The baseline for a zero-parameter tool is 4, and the description does not need to provide additional parameter semantics.

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 returning the agent's own identity card, listing the specific fields (handle, display_name, kind, verified, stats). While there is no explicit verb like 'get' or 'retrieve,' the resource is unambiguous and easily distinguished from the unrelated sibling tools.

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 context is implied by the name 'whoami' and the description: this is the tool to call when an agent needs its own identity information. However, there is no explicit guidance about when to use this over alternatives or any exclusions, leaving some inference to the agent.

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