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

Annotations already disclose readOnlyHint=false, idempotentHint=false and openWorldHint=true, so the safety profile is covered. The description adds only that this action is limited to marketplace services, not travel data. It says nothing about prerequisites, such as needing an offer_id from discovery, whether money is charged or a payment method is required, or what happens when the call is repeated, which both matters because the call is non-idempotent and is not implied by the 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?

The purpose is front-loaded in the first sentence, and the sentences are short. 'Available now' is vague filler that costs space without adding actionable meaning.

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 mutating, open-world tool with four parameters that lack schema descriptions, no output schema, and real cost or side effects, the description is under-specified. It omits required prerequisites (where offer_id comes from), billing implications, the optional `number` parameter, and the shape of the request's effect.

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 explain the four parameters itself. It clarifies form_factor and number_line only by saying they must be 'allowed by the offer'; offer_id's source is never explained, and the optional `number` parameter is never mentioned.

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 and resource: 'Starts a Widely order for a listed marketplace service.' The scope exclusion ('Does not order Widely travel data') helps separate it from travel-related siblings, but it never distinguishes itself from prepare_order, quote_service, or order_esim, which are the closest alternatives.

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?

Steers the agent toward ordering a listed service, with a negative scope rule ('Does not order Widely travel data'), but gives no context about when to call it. It doesn't say whether prepare_order or quote_service must be called first, nor how the tool relates to order_esim.

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