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

The annotations already declare that the tool is read-only, idempotent, open-world, and non-destructive. The description adds real value beyond that by stating that nothing is created and nothing is charged, and that invalid input returns an error code and the field where the problem occurred, which tells the agent what to expect from failures. It does not say whether a quote expires, whether auth or account setup is required, or whether the quote is guaranteed until purchase.

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 with no waste. The outcome (price and breakdown) comes first, the side-effect guarantee comes second, and the failure behavior comes last. Each sentence adds distinct information.

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?

Because there is no output schema, the description should describe return values, and it does partly describe price, breakdown, and the error shape with code and field. However, it leaves the twelve-field nested order payload largely undocumented, so an agent still cannot construct a valid call from the description alone.

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 one nested 'order' object with twelve properties, but schema description coverage is 0% at the top level. The description says only that the tool validates an order and refers to 'the field it is in' for errors. It never explains what the order must contain, which fields are required, or how product, budgets, and targeting interact, so it does not compensate for the schema 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?

The description names a specific action applied to a specific resource: it validates an order and returns its exact price in USD along with a breakdown. The sentence 'Creates nothing and costs nothing' also contrasts quote_ad with create_ad and buy_ad_credit, though it does not name those sibling tools explicitly.

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 use case is only implied: validate an order to learn its price before committing. The description does not explicitly say when to call this tool instead of create_ad, nor does it say the quote must precede creation. There are no exclusions or prerequisites such as an account or credit requirement.

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