stop

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

With no annotations, the description carries the behavioral burden and does disclose the non-obvious fact that cancellation is not terminal — the agent remains resumable via follow_up. It does not say what happens to in-flight work, whether cancellation is graceful, or what permissions are needed, so it is helpful but not complete.

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 zero filler; the action is front-loaded and the resumability caveat follows immediately. Every clause earns its place.

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 tool with no output schema, the description covers what it does and the key follow-on behavior. What is missing is minor — side effects on in-flight execution and any preconditions — but nothing prevents correct invocation.

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 single id parameter is well documented in the schema ("Short agent id, e.g. ag_7f3k2m"). The description adds no additional meaning about the id, 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?

Specific verb ("Cancel") plus specific resource ("an agent's current run"), so the operation is unambiguous. It also names follow_up as the contrasting sibling, letting an agent separate cancellation from resumption without opening either 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?

The description clearly frames the use case (halt an in-progress run) and points to follow_up for the resumption case, giving usable routing context. It stops short of stating explicit exclusions, e.g. when wait or steer would be preferred over stopping.

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