Reply to Comment

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

Annotations already indicate readOnlyHint=false, destructiveHint=false, idempotentHint=false. The description adds context: it operates on behalf of the authenticated channel, supports basic HTML entities in text, and lists specific error codes (400, 403, 404), which are beyond the annotations.

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

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

The description is well-structured with sections (Args, Returns, Example, Errors). Each part serves a purpose, though it could be slightly more concise. It is efficiently organized for an AI agent.

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

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

Given no output schema, the description provides a return schema example. It covers parameters, errors, and the action. It does not explain authentication beyond 'authenticated channel,' but that is sufficient. Overall, it is complete for the tool's usage.

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

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

Schema coverage is 100% with descriptions. The description adds value by noting that text supports basic HTML entities and providing an example (parentId example). This extra semantic detail justifies a 4.

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

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

The description clearly states it posts a reply to an existing top-level comment thread, which is a specific verb+resource. It distinguishes itself from sibling tools like youtube_create_comment_thread (creates a new thread) and youtube_update_comment (edits a reply).

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

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

The description implicitly indicates when to use (to reply to a comment) but does not explicitly mention when not to use or compare with alternatives. It lacks guidance like 'use this for replying, use youtube_create_comment_thread for new top-level comments'.

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