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

Annotations declare destructiveHint=true and idempotentHint=false, so the safety profile is already covered. The description adds real behavioral value beyond that: it discloses the credit-refund behavior ('credits held for work that had not started are released') and the fact that only not-yet-started work is refunded. It stops short of saying whether cancelled in-flight work can be resumed or retried.

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; the primary behavior is front-loaded and the scoped variant is appended as an alternative. 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?

An output schema exists, so return values need not be described. For a destructive, non-idempotent operation with two parameters, the description covers scope and credit release adequately; the only gap is whether the cancellation is reversible or how the caller confirms completion.

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 0%, so the description must carry the load. It meaningfully explains the optional 'video' parameter by describing the two modes (whole board vs. one named video's render), which is exactly the semantic distinction the bare integer schema lacks. 'storyboard_id' is only implied as the target board and gets no explicit description.

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 states a specific verb (stop/cancel) and resource (a storyboard's in-flight generations and renders), and it clarifies the two scopes of cancellation. It does not explicitly disambiguate itself from delete_storyboard or undo_storyboard, so an agent must infer that this halts work without removing the board.

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 rather than stated: the agent learns it cancels everything on the board by default or a single video's render 'when you name it.' There is no explicit when-to-use/when-not guidance and no mention of the relevant siblings (delete_storyboard, undo_storyboard, cancel_workflow_run) that a caller might confuse this with.

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