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

Annotations already declare readOnly, idempotent, non-destructive and open-world behavior, so the safety profile is covered. The description adds genuinely new context beyond them: the billing scope authorization requirement, the fact that the call is free, and that prices are versioned and denominated in USD cents.

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 short sentences, no filler. The resource and scope are front-loaded, and the auth/cost constraints and sibling routing follow in descending priority order.

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?

For a zero-param, read-only tool with no output schema, the description covers what is returned (rate card and action prices), the unit, the auth requirement, and the cost. Only minor details such as response shape or caching/versioning mechanics are absent, which is acceptable here.

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 and has an empty schema, so there is nothing for the description to disambiguate. Baseline for a parameterless tool applies; no parameter-level detail is missing.

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 (read) plus the exact resource (the authenticated environment's versioned rate card and action prices), including the unit (USD cents). It also names the sibling create_quote, so an agent can distinguish this read-only price lookup from the quote-binding tool without opening either schema.

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?

Gives a prerequisite ('Requires billing scope') and routes the agent to create_quote for the follow-on action, which is clear context for use. It stops short of an explicit when-not-to-use statement or a full alternative comparison, so it lands just below the top band.

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