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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds the legacy scope and ledger-vs-aggregate semantic, but does not disclose pagination behavior or how status filtering behaves; this is acceptable but not additive beyond annotations.

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?

Three sentences, each earning its place: scope, contrast with the aggregate endpoint, and API mirror. No filler; key scoping is front-loaded.

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?

Output schema and annotations cover return shape and safety, while the description adds the crucial domain context (legacy-only, ledger rather than aggregate). It does not mention default limit or status implications, but those are visible in the schema, leaving only a minor completeness gap.

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 only 20% (only business_id has a description), and the description does not compensate. From/to are only implicitly tied to 'per-period,' and limit/status are left unexplained. With five optional parameters, this is a notable gap.

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?

Description identifies a specific resource (billing_overage_charges ledger) and scope (legacy per-minute-overage tiers). It explicitly distinguishes this from the aggregate returned by get_balance, so an agent can tell it apart from sibling tools without inspecting 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?

States a clear legacy-only condition and contrasts with get_balance, which only returns an aggregate. This tells the agent when to use this tool and when to prefer a different one, with no ambiguity.

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