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

Annotations already declare readOnlyHint=true, and the description adds useful behavioral context: the call is free, it validates input, and it returns a credit hold estimate plus coverage check. This goes beyond the annotation without contradicting it.

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 two tight sentences, front-loaded with the key fact that the tool is free. Every sentence contributes actionable information about what the tool does and when to use it.

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 no output schema, the description adequately explains the return value: exact credit hold, price basis, and balance coverage. It also communicates the validation behavior and free nature, making it complete for a simple two-parameter quote tool.

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%, with both 'tool' and 'input' documented in the schema. The description reinforces that input is 'the input you intend to send' and that omission gives a default estimate, but it does not add substantial meaning beyond the schema.

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 clearly states the tool validates input for a tool and returns the exact credit hold a real call would take, plus balance coverage. It uses a specific verb ('quote', 'validates', 'returns') and distinguishes itself from paying/executing the call by emphasizing it is free and for budgeting.

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 says to use it to budget before a billed call or to lint an input for free, providing clear usage context. It does not explicitly name alternatives, but the use cases are concrete enough for an agent to know when this tool is appropriate.

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