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

Annotations only declare destructiveHint=true, but the description goes far beyond: it discloses that the request is recorded immediately, returns run_id and cancel_requested=true, that the machine is killed and the run terminalizes as 'killed' on the next orchestration tick (~60 s), and the exact 409 failure condition for collecting runs. That is unusually rich behavioral context for an irreversible operation.

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 sentences, zero filler, front-loaded with the cancellation scope before the error case and the async lifecycle. Every clause carries operational meaning (states, 409, timing, polling).

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 one-parameter mutation with no output schema, the description supplies everything an agent needs: eligible states, the blocking error, the asynchronous completion model with timing, the returned fields, and the polling tool. Nothing material is missing.

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 100% for the single run_id parameter, and the schema already describes it fully, so the baseline 3 applies. The description references run_id only in the return-value context, adding no syntax or format detail beyond the schema.

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 run') and immediately scopes it to 'any non-terminal state before collecting', which distinguishes it from read/collection siblings. An agent can tell exactly what state transition this performs without opening the 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?

Gives explicit when-to-use (non-terminal states), a when-not with the consequence spelled out ('a collecting run's outputs are delivered and charged: 409'), and names the follow-up tool (mcg_get_run) for observing the result. Routes the agent correctly against alternatives.

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