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

The description goes beyond annotations with 'cooperatively' and especially 'completed external actions are not reversed,' which is critical for an agent deciding whether to cancel. No contradiction with 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?

Two concise sentences, front-loaded action, no redundancy. The key caveat is included.

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?

Definitions clear with both params documented, plus the critical non-reversal caveat. Missing only explicit routing to siblings and return expectations, which are not essential for a destructive cancel action.

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 covers both parameters with clear descriptions (IDs returned by modem_agent_invoke). Description adds no new parameter-level meaning beyond 'exact' run targeting.

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 ('cancel') and identifies the exact target ('one exact durable Modem agent run'). It is clearly distinguished from sibling tools like modem_agent_get_run or modem_agent_invoke.

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?

No explicit guidance on when to use this tool versus alternatives, no prerequisites or conditions for cancellation, and no mention of what to check before invoking. The caveat about external actions is behavioral, not usage routing.

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