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

Annotations already mark it read-only and non-destructive, and the description adds meaningful behavioral detail: it is FREE, it only validates/prepares, it produces a requestId and price ceiling, and repeated preparation is discouraged. These details go well beyond the structured annotations without contradicting them.

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 compact, front-loaded with the FREE nature, and every sentence adds value. It packs purpose, constraints, return values, and a usage warning into four short sentences with no fluff.

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 helpfully names the return values: requestId, price ceiling, and exact arguments. It also warns the user to save the prepared call. The main remaining gap is the lack of an explicit response shape or instructions for how to use the requestId in a subsequent paid call.

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 0%, so the description must compensate for the two parameters. It references 'input' generically and implies the prepared call is named by `name`, but it never explains that `input` must conform to the selected tool's schema or how the returned 'exact arguments' relate to the input parameter.

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 ('Validate input') and resource ('one paid call'), and clearly enumerates the return values. It reads as a distinct preparation step rather than an execution tool, so an agent can separate it from sibling operation tools.

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 when-to-use and when-not-to-use guidance: it is FREE, should be done before execution, and must not be repeated to recover an uncertain payment. It also clarifies that it performs no execution, funding, or reservation, preventing misuse.

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