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

Annotations already declare readOnlyHint, non-destructive, and closed-world behavior. The description adds useful behavioral detail beyond annotations: it renders the letter, validates addresses, and returns a widget with a create-draft action. It does not cover permissions or rate limits, but those are less critical for a read-only preview.

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?

Two sentences, front-loaded with the primary action and purpose. Every clause adds information and there is no filler.

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 tool with 17 parameters, nested objects, and no schema descriptions, the description is too sparse. It explains the high-level preview behavior but leaves the agent with little guidance on how to construct the complex address and letter payloads, even though an output schema exists to cover return values.

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% across 17 parameters, many with nested objects and enums. The description only generically references 'letter' and 'addresses' and does not explain required fields such as sender_address_type, recipient_address_type, address ID/text/manual variants, request_id, mail_class, or render options.

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 ('preview'), resource ('letter order draft'), and distinguishes the operation as non-writing. It does not explicitly name sibling tools like create_letter_order_draft, but the preview framing and 'before creating checkout' timing make the purpose clear.

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?

It gives clear timing: use this before creating checkout to prepare a non-writing preview. It does not explicitly say when not to use it or name alternative sibling tools, but the context is sufficient to infer that this is a pre-creation validation step.

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