Cancel a DSH session run

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

Annotations already declare destructiveHint=true and idempotentHint=false, so the safety profile is known; the description adds genuinely new behavior: the in-flight prompt settles with stopReason "cancelled" and no other session is affected. It names the underlying ACP session/cancel call and clarifies the effect on running work, though it omits the post-cancel session state (still open? resumable?).

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, front-loaded with the action and its scope, with no redundant restatement of the name or schema. Every clause carries information.

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 destructive tool with annotations covering the safety profile and no output schema, this is nearly complete: it explains what happens to running work and the isolation guarantee. The remaining gap is the resulting session lifecycle state, which matters given the dsh_resume_session and dsh_close_session siblings.

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 session_id parameter, which is already documented as the explicit session id to cancel. The description's 'exactly one session' reinforces the cardinality but adds no format or lookup guidance beyond the schema, so the baseline 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?

States a specific verb (cancel/stop the work) and resource (one session), and the phrase 'exactly one session' plus 'other sessions are untouched' pins the blast radius. It does not explicitly distinguish itself from the sibling dsh_close_session, which a reader could plausibly confuse with cancellation.

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?

Usage is implied by 'stop the work of exactly one session', which suggests interrupting a running prompt, but there is no explicit when-to-use versus when-not guidance. It never says whether to prefer this over dsh_close_session or whether the session can be resumed afterward with dsh_resume_session.

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