Billing Ledger

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

Annotations already indicate readOnlyHint=true and destructiveHint=false. The description adds meaningful context beyond that: the auth requirement ('Requires billing read access'), an explicit no-side-effects disclaimer ('does not initiate purchases or evaluations'), and pagination behavior via cursor reuse. This fully discloses the tool's behavioral profile.

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 earns its place: purpose, sibling differentiation, default/override behavior, response shape, and auth/safety caveat. Information is front-loaded with the verb and resource first, followed by routing. No filler or repetition of schema content.

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 an output schema present, return values need no extra description beyond the pagination fields already mentioned. The description covers purpose, alternatives, default window, parameter interactions, pagination, permissions, and side-effect safety. For a 12-parameter optional tool, all non-obvious decision points are addressed.

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?

Input schema covers 100% of parameters, so baseline is 3. The description adds semantic value by relating range to startAt/endAt ('explicit timestamps override the corresponding range bounds') and by explaining cursor usage ('reuse the cursor with the same filters'), which deepens understanding without restating schema details.

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 specific verb and resource: 'Inspect individual Cloudeval usage attempts and credit charges for the authenticated account.' It also explicitly differentiates from sibling billing_usage by noting that tool is for aggregates, so an agent can distinguish them without opening schemas.

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 gives explicit routing guidance: 'Use billing_usage for aggregates or billing_invoices for payment receipts.' It also provides conditional context like the default 30-day window and how timestamps override range bounds, making the when-to-use clear.

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