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YouTube MCP

YouTube MCP

by pratikgh0se
OverviewSchemaSourceRelated ServersDiscussionsAdmin
TypeScript
Local

youtube_preflight_caption_update

Destructive

Validate and preview an owned YouTube caption update before applying changes, checking the video ID, caption file, language, MIME type, and track details.

Instructions

Validate and preview an owned caption update.

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": {
      "videoId": "<videoId>",
      "filePath": "<filePath>",
      "mimeType": "<mimeType>",
      "language": "<language>",
      "name": "<name>",
      "captionId": "<captionId>"
    },
    "name": "youtube_preflight_caption_update"
  }
}

Input Schema

NameRequiredDescriptionDefault
nameYesCaption track name shown to viewers, up to 150 characters.
isDraftNoWhether the caption track is a draft that is not shown to viewers.
videoIdYesID of an owned video the caption belongs to.
filePathYesAbsolute path to the local caption file.
languageYesCaption language code, e.g. en.
mimeTypeYesCaption file MIME type: application/octet-stream, application/ttml+xml, text/plain or text/vtt.
captionIdYesCaption track ID, from youtube_list_caption_tracks.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed7 schema fields changedv0.3.1
    • addedInput schema / properties / captionId / description
      Added value: +"Caption track ID, from youtube_list_caption_tracks."
    • addedInput schema / properties / filePath / description
      Added value: +"Absolute path to the local caption file."
    • addedInput schema / properties / isDraft / description
      Added value: +"Whether the caption track is a draft that is not shown to viewers."
    • addedInput schema / properties / language / description
      Added value: +"Caption language code, e.g. en."
    • addedInput schema / properties / mimeType / description
      Added value: +"Caption file MIME type: application/octet-stream, application/ttml+xml, text/plain or text/vtt."
    • addedInput schema / properties / name / description
      Added value: +"Caption track name shown to viewers, up to 150 characters."
    • addedInput schema / properties / videoId / description
      Added value: +"ID of an owned video the caption belongs to."
  2. First observedv0.1.0

TDQS

B3.1/5.0
Behavior2/5

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

Annotations declare destructiveHint=true, yet the description frames the tool as 'validate and preview', which reads as a safe dry-run — a direct tension the description does nothing to resolve. It also omits what the preview returns (pass/fail? a plan/token consumed by youtube_update_caption?) and whether it can affect the live caption at all.

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

Conciseness4/5

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

A single six-word sentence with no wasted clauses and the verb front-loaded. The brevity is efficient, though it shades into under-specification given the tool's complexity.

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

Completeness2/5

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

With 7 parameters, no output schema, and a paired sibling mutation, the description should explain what the preview yields and how it relates to youtube_update_caption. Neither is covered, so an agent knows the tool's name but not what to do with its result.

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?

Schema description coverage is 100%, so every one of the 7 parameters (including the captionId cross-reference to youtube_list_caption_tracks and the mimeType enum) is already documented in the schema. The description adds no syntax, constraints, or interaction between filePath/mimeType that would go beyond the schema, so the baseline 3 applies.

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

Purpose4/5

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

Names a specific verb pair ('Validate and preview') and resource ('an owned caption update'), which lets an agent distinguish it from the real mutation (youtube_update_caption) and from youtube_preflight_caption_upload/delete. It stops short of naming those siblings explicitly, so the differentiation is inferable rather than stated.

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 word 'preflight' plus 'preview' implies this is a dry-run step to call before youtube_update_caption, but the description never says that, never states when the preflight is required versus optional, and never names the alternative. Usage is only implied.

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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