Balance, usage and your prices (free)

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

Annotations carry readOnlyHint, openWorldHint, and idempotentHint, but the description adds a critical behavioral disclosure those fields do not cover: 'FREE — this call never spends credits.' This cost/credit trait is exactly the kind of context that structured annotations fail to convey, and it materially affects whether an agent should call the tool.

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?

Four sentences, each carrying a distinct and necessary piece of information: what it returns, that it costs no credits, when to call it (before/after paid batches), and why its price data is authoritative. The content is front-loaded with the result set, and there is no filler — only a minor, acceptable echo of the title's 'free'.

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?

An output schema exists, so return values need no description-level explanation. All five parameters are optional and fully documented in the schema, annotations cover the read-only/idempotent safety profile, and the description covers purpose, cost behavior, and usage timing. Nothing an agent needs to invoke this tool 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?

Schema description coverage is 100%, so the baseline of 3 applies. The description reinforces the tool's domain (balance, usage, real prices) but does not add per-parameter meaning beyond what the input schema already documents; each parameter already has a thorough description in the schema, including the 'Free' note on include_usage.

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 opens with a precise statement of what the tool returns — account balance, month-to-date usage, and the account's real per-operation prices — using a specific verb-plus-resource pairing that is unambiguous. It clearly distinguishes itself from all 16 sibling tools, which are company/lead data operations, and the 'THIS account's real per-operation prices' phrase adds differentiation from generic list prices.

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?

Provides explicit when-to-call guidance: call it before a batch of paid work to tell the user what they can afford, and after to report exactly what was spent. The closing note that returned prices beat any tool-description list prices also routes the agent to prefer this tool's data over static price figures. For a tool with no true sibling alternative, this fully answers the when/why-to-use question.

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