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

Annotations already declare readOnlyHint/idempotentHint/destructiveHint=false, so the safety profile is covered; the description's 'Read only' is largely redundant. However, it adds genuinely new behavioral context beyond annotations: the white-label visibility rule and the fact that plan changes must be routed to get_upgrade_link rather than performed here. It stops short of mentioning auth/permission needs or what happens when no subscription exists.

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 tight sentences, front-loaded with the substantive content (what data is returned) before the caveats and the alternative tool. No filler or restatement of the title.

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 output schema, the description carries the return-value burden and does so by enumerating the fields delivered. Combined with the visibility caveat and the pointer to the mutation tool, an agent has everything needed to call this correctly and interpret its scope.

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?

There is a single required parameter ('site') and schema description coverage is 100%, with the schema already listing the valid site value. The description mentions 'The site's subscription' but adds no format or selection guidance beyond the schema. Baseline 3 is appropriate when the schema carries the parameter burden.

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 names the exact resource (the site's subscription) and enumerates the concrete fields returned — plan, status, trial, renewal date, cancel-at-period-end, failed-payment freeze — plus the available upgrade plans. It also separates itself from the sibling get_upgrade_link by naming it as the tool for changing plans. An agent can tell what this returns without opening the schema.

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?

It gives an explicit alternative and its trigger ('Use get_upgrade_link to change plans in the browser'), which tells the agent what this tool does NOT do. It also states a when-not condition: the tool is hidden for white-label customers whose partner bills them, so an agent knows results may be absent for those accounts.

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