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

Annotations already establish the safety profile (readOnlyHint, idempotentHint, non-destructive, non-open-world), so the bar is lower. The description adds real value by disclosing what is returned — plan, subscription status, trial end date and allowances — which is otherwise unavailable since no output schema exists. It stops short of stating return format or freshness.

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?

A single, front-loaded sentence with zero filler. The most important information (this shows billing status) leads, and the enumerated contents follow compactly.

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 is the sole carrier of return-value information, and it does enumerate the key fields. What remains thin is guidance on related billing tools, which matters given the three other billing-adjacent siblings.

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 per the rubric this scores at the baseline of 4. There is nothing for the description to disambiguate.

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 ('Show') and enumerates the exact resource contents: plan, subscription status, trial end date, allowances. An agent can immediately tell this apart from get_billing_portal_link (a redirect link) or get_checkout_link (a purchase flow), though the description never names those siblings to reinforce the distinction.

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?

No when-to-use, when-not-to-use, or prerequisite guidance is given. The description never mentions the closely related get_billing_portal_link or get_checkout_link, so the agent must infer from the resource name alone which billing tool to pick.

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