Cancel a ComfyUI job by prompt ID to remove pending tasks or interrupt active generations. Without an ID, stops the currently running job.
Cancel a job: removes it from the queue if pending, interrupts it if running. Without prompt_id, interrupts whatever is running now.
| Name | Required | Description | Default |
|---|---|---|---|
| prompt_id | No |
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description goes beyond the destructiveHint annotation by specifying exactly what happens in each state: pending jobs are removed from the queue, running jobs are interrupted, and omitting prompt_id affects the currently running job. This is valuable behavioral context and does not contradict the annotation.
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 cover the action, the conditional behavior, and the default behavior without any wasted words. The most important information is front-loaded.
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?
Given a single optional parameter, a destructiveHint annotation, and an output schema, the description provides all necessary operational details: what the tool does, how it behaves for pending versus running jobs, and how prompt_id affects targeting. Nothing essential 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?
With 0% schema description coverage, the description compensates by explaining the meaning of omitting prompt_id and implying that prompt_id identifies the specific job to cancel. It could more explicitly state where to obtain prompt_id, but the core semantic is clear.
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 resource ('a job'), and clearly distinguishes the two behaviors: removing a pending job from the queue or interrupting a running job. It is unambiguous and distinct from sibling tools, none of which are cancellation tools.
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 description provides clear context for when to use the tool and how to target a specific job versus the currently running one. It does not explicitly mention alternatives, but no alternative cancellation tool exists among the siblings, so the omission is acceptable.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.