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

Annotations already declare destructiveHint=true, idempotentHint=true, and readOnlyHint=false, covering the safety profile. The description adds two useful facts beyond structured data: the order must be 'resting' (unfilled) and an API key is required. It still omits failure behavior for already-filled or unknown orders.

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 short sentences with the action front-loaded and no wasted words. Brevity is appropriate for a one-parameter tool, though the second sentence is a precondition rather than usage guidance.

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 simple mutation tool with annotations covering safety and idempotency, the description is minimally adequate: it names the action, the API key requirement, and the resting-order constraint. It lacks any return/failure semantics and gives no help locating the order_id, leaving an agent partially equipped.

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 coverage is 0% and the single parameter order_id is undocumented in the schema; the description offers no help on its format or where to obtain it (e.g., from paper_orders). With one non-trivial parameter, the description should compensate but does not.

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 (cancel a resting limit order) and narrows scope with the qualifier 'resting', which distinguishes it from position-closing siblings like paper_close. It does not name or distinguish itself from paper_modify_order or paper_close explicitly, so differentiation is only partial.

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 only guidance is a precondition ('Requires an API key'), which is not a when-to-use rule. There is no indication of when to cancel versus modify (paper_modify_order) or close (paper_close), nor what happens if the order has already filled.

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