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Cancel Job

cancel_job

Stop a stuck or unwanted running command by killing its process inside a Docker sandbox. If the job already finished, it returns the final state unchanged.

Instructions

Stop a running command and kill its process inside the sandbox.

USE THIS when a command is clearly stuck or no longer needed. Safe on a job that already finished -- it returns the final state untouched.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "job_id": "<job_id>"
    },
    "name": "cancel_job"
  }
}

Input Schema

Name	Required	Description	Default
`job_id`	Yes	Job id to cancel.

Output Schema

Name	Required	Description	Default
`error`	No
`job_id`	Yes
`status`	Yes
`stderr`	No
`stdout`	No
`command`	Yes
`exit_code`	No
`duration_ms`	No
`experiment_id`	Yes
`stderr_truncated`	No
`stdout_truncated`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 8, 2026

TDQS

A4.2/5.0

Behavior4/5

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

With no annotations, the description carries the full burden. It discloses that cancellation kills the process and that calling it on a finished job is safe and returns the final state untouched. This covers the key behavioral expectations, though it does not mention side effects like partial artifacts or queued jobs.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is compact and well-structured. It leads with the core action, then gives a direct usage condition, and closes with an important safety note. No wasted words.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The tool has one simple parameter and an output schema, so the description does not need to explain return values. It sufficiently covers action, usage, and safety. Some edge cases, such as cancelling a queued versus running job, are not addressed, keeping it just short of a 5.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The input schema already documents job_id as 'Job id to cancel' with 100% coverage. The description does not add additional meaning about the parameter, so the baseline score of 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description uses specific verbs ('stop', 'kill') and names the resource ('a running command inside the sandbox'). It clearly differentiates this from sibling tools like get_job_status or get_job_result by focusing on cancellation rather than inspection.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explicitly says when to use it: when a command is 'clearly stuck or no longer needed'. It also gives a helpful safety condition about already-finished jobs. It does not explicitly name alternatives or exclusions, so it misses the top score.

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

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