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

Annotations already declare destructiveHint=true, idempotentHint=true, and openWorldHint=true, but the description adds material context: the unknown-outcome hazard (the order may have executed), the no-retry-with-new-id rule, and a prompt-injection warning that broker/hook/human text arrives as untrusted data. It is consistent with the annotations rather than contradicting them.

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 dense sentences, front-loaded with the action, then the failure-mode rule, then the safety warning. No filler or restatement of the name; each sentence carries an operational rule the agent must obey.

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 destructive, open-world mutation with no output schema and no sibling-differentiation gap, the description covers risk and follow-up calls well. Its only gap is that it references an `unknown` outcome field without describing the return shape, which the absent output schema leaves entirely to inference.

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 100%, so all four parameters (reason, order_id, account_id, client_request_id) are already fully documented in the schema, including the idempotency semantics of client_request_id. The description adds no parameter-level detail beyond what the schema provides, so the baseline of 3 applies.

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 first sentence states a specific verb and resource with scope ('Cancel a pending order'), which cleanly separates it from siblings like close_position (closing an open position), modify_order, and place_order. An agent can select this tool 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?

It gives explicit conditional guidance: on an `unknown` outcome, never retry with a new client_request_id, and call get_trade_status and get_positions/get_orders first. This is a clear when-not plus named alternatives, exactly the routing information an agent needs before retrying a destructive call.

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