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

Annotations already declare destructiveHint=true and readOnlyHint=false. The description adds context by specifying that the run is 'finalized as failed with a custom message', which is not captured in annotations. It also implicitly indicates that cancellation changes the run's terminal state, adding value beyond the annotations.

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?

The description is two sentences, front-loads the action, and contains no redundant words. It efficiently conveys the purpose and the result with minimal length.

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 single-parameter tool with an output schema and annotations covering destructive and idempotent behavior, the description covers the essential conditions (which states are cancellable) and the outcome. It does not elaborate on error cases or prerequisites, but such detail is not critical given the tool's simplicity.

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% and the parameter run_id is already documented with its type and pattern (trun_...). The description does not add any extra semantic detail about the parameter, so the baseline score 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 description uses a specific verb ('stop') and resource ('a run') and clearly enumerates the applicable states (pending, running, waiting for input). It also states the outcome (finalized as failed with 'Cancelled by the caller'), which distinguishes it from sibling tools like get_run or wait_for_run.

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 gives clear context on when the tool is applicable by listing the run states it can stop. It does not explicitly mention exclusions or alternatives, but the sibling set makes the use case obvious, and the stated states imply that already-completed runs are out of scope.

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