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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the mutation risk is covered structurally. The description adds real value beyond them by disclosing that cancellation returns billing metadata and that only active runs are eligible, which an agent needs to anticipate the side effect and the precondition.

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?

A single front-loaded sentence with the action first and the notable side effect second. No filler, no redundancy.

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 destructive tool with no output schema, the description conveys the key return hint (billing metadata) and the active-run precondition, but omits whether cancellation is reversible, idempotent, or what error surfaces on a non-active run. Adequate but with clear gaps given the destructive nature.

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?

Only one parameter and schema description coverage is 100%, so the schema already documents run_id fully. The description's 'active workflow run' merely echoes the schema wording and adds no format, sourcing, or retrieval guidance, so it sits at the baseline.

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) and resource (workflow run), and distinguishes itself from sibling mutators like retry_workflow_run and continue_workflow_run by the 'active' qualifier. It also signals a side effect (billing metadata), though it doesn't name a sibling it is explicitly not.

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 when-to-use guidance, no prerequisites (e.g., run must be in an active state), and no contrast with alternatives such as retry_workflow_run or cancel_job. The agent must infer applicability from the name and the word 'active' alone.

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