whoami

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

With no annotations, the description carries the full burden. It states the tool returns identity information, which implies a read-only operation, but it does not explicitly say it has no side effects, require authentication (though 'authenticated' is mentioned), or disclose error behavior. It provides minimal but sufficient transparency for a simple query tool.

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, focused sentence that front-loads the verb and clearly states the returned data. It has no filler or redundant wording.

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?

The tool is extremely simple (no parameters) and has an output schema, so the description does not need to explain return values. It fully states what the tool does, making it complete for an agent to invoke correctly.

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, so there is nothing to explain. The description need not add parameter details; the baseline of 4 applies because there are no parameters for the schema to cover.

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 specific verb ('Return') and a specific resource ('authenticated principal, tenant, and effective RBAC scopes'). It clearly distinguishes from all sibling tools, which focus on data assets, DAGs, and logs, none of which relate to identity or access.

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 does not explicitly state when to use this tool versus alternatives, but its purpose is so distinct that usage is implied. There is no mention of context such as 'call this at session start' or 'use this before making other calls to verify permissions,' leaving the agent to infer the appropriate timing.

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