Cancel a pending or active ComfyUI job using its ID: removes it from the queue or interrupts it if running.
Cancel one of this server's own jobs: removes it from the ComfyUI queue or interrupts it if running.
| Name | Required | Description | Default |
|---|---|---|---|
| job_id | Yes |
| 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?
No annotations are provided, so the description carries the behavioral disclosure burden. It correctly discloses the core action and its two possible effect paths, but it does not mention edge cases like what happens if the job is already finished, whether cancellation is idempotent, or whether partial outputs are preserved.
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, dense sentence that front-loads the action and scope, then explains the two possible behaviors. Every part is informative and there is no filler.
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?
The tool is simple with one required parameter and an output schema available, so the description need not cover return values. It provides enough context for an agent to choose and invoke the tool correctly, though it omits minor details like failure modes and whether partial results remain accessible.
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 0% because job_id has no description. The description indirectly clarifies that job_id must identify 'this server's own jobs,' which adds some meaning beyond the raw schema, but it does not specify the expected format, where to obtain a valid job_id, or any constraints on the value.
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' with a clear resource: 'one of this server's own jobs.' It explicitly states the two behavioral outcomes (removing from queue or interrupting if running), which fully differentiates it from siblings like job_status, wait_for_job, and fetch_result.
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 clearly establishes the context of use: canceling a job on this server. It implies a scope constraint ('this server's own jobs') but does not explicitly name alternatives or say when not to use this tool, such as checking job status first or waiting instead of canceling.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.