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Cancel Task

cph_task_cancel

Idempotent

Cancel a task no longer needed, transitioning it from pending, in_progress, or blocked to cancelled. Optionally provide a reason.

Instructions

Cancel a task that is no longer needed.

State machine: pending | in_progress | blocked → cancelled

Args:

task_id: The task to cancel
reason: Why the task is being cancelled (optional but recommended)

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": {
      "task_id": "<task_id>"
    },
    "name": "cph_task_cancel"
  }
}

Input Schema

Name	Required	Description	Default
`task_id`	Yes
`reason`	No	Why is this task being cancelled?

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.6.0Jun 13, 2026

TDQS

A4.2/5.0

Behavior4/5

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

The description reveals the state transition behavior, which adds context beyond annotations. Annotations provide idempotentHint=true, and the description confirms the effect (cancelling). No contradiction. However, it does not detail side effects like what happens to dependent tasks.

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 extremely concise, using a state machine notation and two bullet points. Every sentence adds value, and the structure is front-loaded with the main action.

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?

For a cancellation tool with moderate complexity, the description covers the state machine and parameter recommendations. It does not include return values or error handling, but the absence of an output schema and the idempotent hint mitigate this gap.

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

Parameters4/5

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

Schema coverage is 50% (task_id lacks description). The description adds 'The task to cancel' for task_id and 'optional but recommended' for reason, which provides meaningful guidance beyond the schema's label for reason.

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 specifies the verb 'Cancel' and resource 'task' clearly. The state machine transitions (pending|in_progress|blocked -> cancelled) further clarify the scope, distinguishing it from sibling tools like cph_task_create or cph_task_start.

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

Usage Guidelines3/5

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

The description implies use when a task is 'no longer needed' and the state machine shows valid starting states, but it does not explicitly state when not to use the tool or compare with alternatives (e.g., cph_task_update). Guidance is present but not exhaustive.

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