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felipefontoura

YouTube MCP Server

youtube_post_comment

Post a new top-level comment on a YouTube video by providing the video ID and comment text, enabling direct audience engagement and discussion participation.

Instructions

Post a new top-level comment on a video.

Args: video_id: YouTube video ID to comment on text: Comment text

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
textYes
video_idYes
Behavior2/5

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It mentions neither that posting requires OAuth/auth state, that comments are subject to YouTube moderation/spam filtering, that the comment is public immediately, nor what happens on failure. The description is just a bare directive with no behavioral context.

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?

Reasonably concise - a single-sentence purpose followed by two simple parameter lines. There is no wasted verbiage. However, it could be slightly more structured with clearer separation between the action and parameter documentation, but the brevity is acceptable.

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?

This is a write/mutation tool with no annotations and no output schema. The description offers almost no context: it doesn't explain authentication requirements, rate limits, moderation outcomes, reply behavior, or error cases. For a tool that posts content publicly, significantly more behavioral context is needed.

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 0%, so the description must compensate for documenting the parameters. It does list both parameters (video_id and text) with one-line descriptions of what each is. However, it doesn't add format details (e.g., max text length, whether video_id format matters), but 'video_id: YouTube video ID' and 'text: Comment text' are minimally adequate labels.

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?

The description clearly states 'Post a new top-level comment on a video' with a specific verb ('post'), resource ('comment'), and scope ('top-level'). It distinguishes from the sibling tool youtube_reply_to_comment by specifying 'top-level', which meaningfully differentiates the action.

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

Usage Guidelines2/5

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

No guidance on when to use this tool vs alternatives. It does not mention that youtube_reply_to_comment is for threaded replies, does not state prerequisites like needing authentication (youtube_auth), or any limitations. The 'top-level' qualifier offers implied differentiation but no explicit when/when-not guidance.

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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