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web_task_cancel

Idempotent

Stops a task using its owning API key, or its legacy access_token. No new operations start. Cancellation is free; unused account credit reservations are released. Cancelling a finished task changes nothing.

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": {
      "id": "<id>"
    },
    "name": "web_task_cancel"
  }
}

Input Schema

Name	Required	Description	Default
`id`	Yes	The task id, from web_task_start.
`access_token`	No	Task-scoped access token returned by web_task_start; not an API key.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 17, 2026

changedInput schema / required

Previous value: -[
-  "id",
-  "access_token"
-]New value: +[
+  "id"
+]

Changed2 schema fields changedOct 12, 2026

addedInput schema / properties / access_token

Added value: +{
+  "description": "Task-scoped access token returned by web_task_start; not an API key.",
+  "type": "string"
+}

changedInput schema / required

Previous value: -[
-  "id"
-]New value: +[
+  "id",
+  "access_token"
+]

AddedOct 12, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Annotations already establish non-read-only, idempotent, non-destructive behavior, so the description earns credit for going further: cancellation is free, in-flight credit reservations are released, no new operations start, and the finished-task no-op case. It does not cover failure modes (invalid/expired token, unknown id) or the response shape.

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?

Four short, front-loaded sentences; the action and auth mode come first, then cost and no-op behavior. No filler or restatement of the tool name.

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?

With no output schema, the description must stand alone, and it covers cost, credit release, and the no-op case well. It leaves error conditions and what the caller receives after a successful cancel unspecified, which for a mutation tool is a modest gap rather than a severe one.

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 100%, so the baseline is 3, but the description adds real meaning: the credential is the task's *owning* API key and the access_token is explicitly the legacy/alternate path. The schema alone labels access_token but does not convey the two-auth-mode relationship the description clarifies.

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?

States a specific verb and resource ('Stops a task') plus the ownership mechanism ('using its owning API key, or its legacy access_token'). This is unambiguous and immediately separable from siblings like web_task_start and web_task_status within the web_task_* family.

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?

Usage context is only implied. The description notes that cancelling a finished task 'changes nothing', which hints at when the call is pointless, but it never says when to cancel versus checking web_task_status first, nor names any alternative tool or prerequisite ordering.

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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