Billing status

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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description reinforces this with 'Read-only, free'. It adds critical behavioral context beyond annotations: the price field nuance (billing per plan.period, not monthlyUsd), the member-specific visibility limitation (billingScope:'member'), and the instruction to never tell a member there is no card because it cannot be seen. This is exactly the kind of hidden behavior agents need to know.

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 dense but every sentence earns its place: it leads with the core purpose, then details the specific fields, then the critical usage caveats. The shared-workspace warning and the instruction about not misreporting card status are essential to correct agent behavior. It is structured front-loaded and thorough without fluff.

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 zero required parameters and no output schema, the description must fully explain what the tool returns and any caveats. It covers the plan, balance, auto-reload, card, admin rights, and the nuanced member view. It also explains when to use it relative to other tools. 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?

There are zero parameters, so the schema carries no parameter documentation. Per the rubric, 0 params gives a baseline of 4. The description does not need to add parameter meaning since there are none, and it correctly focuses on the output and usage context instead.

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 clear verb and resource: 'Show this account's billing at a glance' and enumerates the specific data returned (plan id/label/price, credit balance, auto-reload, card on file, admin rights). It explicitly distinguishes itself from sibling tools by saying to call it before upgrade_plan / set_auto_reload, so an agent can easily tell it apart.

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 explicitly tells the agent when to use it: 'Call it before upgrade_plan / set_auto_reload' and explains that members have read-only billing, so they cannot change billing. It also provides conditional guidance for shared team workspaces, telling the agent exactly what a member sees and how to answer honestly. This is explicit and actionable.

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