Cancel a queued or running job by ID, optionally with a reason. Running jobs receive SIGTERM via worker signal poll within about 2 seconds.
Cancel a job (queued → cancelled; running → SIGTERM via worker signal poll, ~2s).
| Name | Required | Description | Default |
|---|---|---|---|
| job_id | Yes | ||
| reason | No | Why — recorded on the broker's job_cancelled event (see jobd_events). |
Changes observed during successful MCP inspections.
v0.5.47Input schema / additionalPropertiesAdded value: +falseInput schema / properties / reason / descriptionAdded value: +"Why — recorded on the broker's job_cancelled event (see jobd_events)."v0.5.5Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the behavioral transparency burden on its own. It discloses meaningful state-dependent behavior: queued jobs are cancelled, and running jobs receive SIGTERM via a worker signal poll in about 2 seconds. It does not cover idempotency, auth, or failure conditions, but the core cancellation semantics are clearly exposed.
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?
The description is a single dense sentence that front-loads the primary action and immediately clarifies state-dependent behavior. There is no filler, and the parenthetical adds crucial implementation detail without bloating the text.
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 description is adequate for a simple cancellation operation, but gaps remain. It does not explain the response/acknowledgement behavior, what happens if the job is already in a terminal state, or how cancellation relates to the sibling jobd_preempt. Given that there is no output schema to compensate, these missing contextual details keep it below a 4.
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 50%, and the description adds little parameter-level meaning. 'Cancel a job' implicitly identifies job_id as the target job, but the description does not elaborate on job_id or reason. The reason parameter is already described in the schema, so the description itself contributes minimal semantic value beyond the schema.
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 and resource: 'Cancel a job'. It further clarifies the two main job states and what happens to each, which is more informative than a generic 'cancel job'. However, it does not explicitly distinguish itself from the sibling jobd_preempt, so it does not earn a 5.
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 gives no explicit guidance on when to use this tool versus alternatives such as jobd_preempt or jobd_submit. It implies usage through its name and purpose, but the agent is left to infer the appropriate context, and no exclusions or alternative routing are provided.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.