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

Annotations already carry the destructive profile (destructiveHint=true, readOnlyHint=false), so the bar is lower; the description still adds real value by scoping what is NOT destroyed (recorded route and measurements survive) and what the caller must supply (a truthful reason). It stops short of saying whether cancellation is reversible or who may cancel.

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 tight sentences with zero filler, and the key differentiator (preservation of route/measurements) is front-loaded before the input requirement. Nothing could be cut without losing 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 two-parameter mutation with no output schema and full annotation coverage, the description supplies the essential contract: what gets cancelled, what survives, and that a reason is mandatory. It omits post-cancellation state and any permission requirement, but nothing critical is missing.

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% with only two parameters, so the schema already documents runId and reason fully. The description only echoes the reason requirement with added emphasis on truthfulness, adding little beyond the structured fields; baseline 3 is appropriate.

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) with an explicit scope qualifier: only an open run, and the route/measurements are preserved. That implicitly separates it from delete_workflow and resume_workflow, though no sibling is named outright, so it falls just short of the top band.

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 phrase 'open workflow run' implies the precondition that the run must still be in progress, and 'A truthful reason is required' signals a mandatory input. But there is no explicit when-to-use vs. when-not guidance and no pointer to delete_workflow for permanent removal, so usage must be inferred.

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