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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds a trait the annotations do not express — that the call succeeds for unauthenticated guests, meaning no auth prerequisite. It stops short of stating rate limits or what a guest response omits, which keeps it from a 5.

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?

Two short sentences, front-loaded with what the caller gets back, with the guest-access caveat appended where it belongs. No filler and nothing repeated from structured fields.

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?

With no input parameters and no output schema, the description carries the burden of describing the return content, and it does: plan, usage against limits, and where to upgrade or get a key. What is missing is the shape of that data (e.g. whether limits are absolute or remaining) and guest-specific omissions, but the essentials are present.

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 takes zero parameters, so the baseline is 4 and there is nothing for the description to disambiguate or compensate for. No parameter claims are made that could mislead.

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?

States a specific verb and resource: shows current plan, usage against limits, and where to upgrade or obtain a key. That is far more concrete than the bare name. It does not name any sibling, but the sibling set (page management tools) contains nothing overlapping, so differentiation is implicit rather than needed.

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?

'Works for guests too' gives an eligibility condition, which implies this is the tool to reach for when checking plan/quota state with or without credentials. However, there is no explicit when-to-use framing, no exclusion, and no named alternative — usage is inferred from the purpose rather than stated.

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