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

Annotations only declare destructiveHint=false, so the description carries most of the burden, and it delivers real behavioral context: the tool emits a matching execution report back to the user's engine, and cancel is clarified as 'cancel the remaining quantity'. It omits permission requirements, whether prior actions can be undone, and error behavior.

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 tight sentences with the action set front-loaded and the downstream side effect trailing; every clause earns its place and nothing is padded.

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 three-required-param mutation tool with no output schema, the definition is serviceable but leaves a gap: it says the execution report goes to the user's engine rather than stating what this tool itself returns, and gives no guidance on failure modes. Adequate, but not complete.

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 67% and the action enum values are already listed in the schema, but the description adds semantic meaning for three of them ('fill (full execution)', 'partial (partial fill)', 'cancel (cancel the remaining quantity)'), which the bare enum does not convey. sessionId and clOrdId get no extra treatment beyond the schema's tag-11 note.

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?

Names a specific verb and resource ('act on one order'), enumerates the four possible actions, and scopes it to a single order 'the user sent in'. It clearly separates itself from list/get siblings like sandbox_get_orders. It does not, however, distinguish itself from fixsim_act_on_orders, which appears to overlap.

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 phrase 'Play the exchange for one order the user sent in' implies the sandbox-simulation context and when this is used, but there is no explicit when/when-not statement or named alternative (e.g., fixsim_act_on_orders vs this sandbox variant). 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.