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

The annotations already indicate read-only and non-destructive behavior, but the description adds critical behavioral context: anonymous users are valid (returned as 'guest'), the semantics of previous_guest and linked_at fields, and guarantees about never returning other parties' data or secrets. This goes well beyond what annotations provide.

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 efficient and well-structured. It leads with the core purpose, then expands on edge cases and semantics without redundancy. Each sentence contributes new, necessary information for correct invocation.

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 that the tool has no parameters and no output schema, the description fully covers the return values (role, language, company, plan) and important nuances (anonymous handling, linking behavior). Nothing an agent needs to call it correctly 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 tool has zero parameters and the schema coverage is 100% (trivially satisfied). The baseline for 0 params is 4, and the description correctly avoids adding parameter-specific info since none exist.

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 states the tool's function: it reports the current user's role, interface language, and (when signed in) company and plan. This is specific to the viewer, distinguishing it from the sibling tools that handle other domains like products or HTS codes.

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 makes it obvious this tool is used when an agent needs to know who it is acting for, but it does not explicitly mention alternatives or exclusions. Given the tool's unique scope, the context is clear enough without explicit 'when not to use' guidance.

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