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

Annotations declare readOnlyHint=false but destructiveHint=false, which is ambiguous on its own; the description resolves that tension by stating twice that nothing is sent and that this only prepares. It also discloses the internal checks performed (filled, not expired) and the concrete content of the preview, including the exercise fee. That is meaningful context beyond the structured fields.

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?

Front-loaded and short, leading with the verb and resource before the details. The closing 'Does not send anything. Prepares only; never sends.' says the same thing three times and could be compressed to a single clause without losing force.

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?

There is no output schema, and the description does a reasonable job of covering the return: a pay/receive preview with fee and a Positions link. It never lists the preview fields or states whether the preview is a string, object, or link set, and it leaves the id's origin unstated, so a little is still missing for a transaction-preparation 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 0% and the single parameter 'id' is documented nowhere. The phrase 'a held option' weakly implies the id identifies the held option position, but the description never says which entity the id refers to, what format it takes beyond the pattern, or where the agent obtains it (e.g. from get_positions). The description therefore does not compensate for the coverage 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?

States a specific verb and resource ('prepare exercising a held option') and then enumerates what the preparation actually consists of: fill/expiry validation, a pay-and-receive preview including the exercise fee, and a Positions link. That is distinguishable at a glance from siblings like prepare_buy or get_positions without opening any schema.

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 implies the precondition for use (the option must be filled and unexpired) and makes clear this is a preview step, not the final action. However, it never names a sibling or a follow-up tool for actually executing the exercise, and gives no explicit 'do not use when' guidance. Usage is inferable rather than stated.

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