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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered; the description adds real behavioral detail beyond that — reply threading via parentId, platform-specific pagination (TikTok/YouTube only), and that held-for-review YouTube comments appear with isHidden true. It does not discuss auth, rate limits, or failure modes, so it is strong but not exhaustive.

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?

Four dense sentences, front-loaded with the core operation and then the non-obvious rules. The clause 'with the account's recent posts' is somewhat ambiguous about whether it describes a filter or part of the response, and one sentence of that ambiguity keeps it below a 5.

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?

With no output schema, the description carries the return-shape burden and does disclose the notable fields (parentId, isHidden) and pagination mechanics. Coverage of what a normal comment object contains and how the account's recent posts factor in is thin, so it is nearly but not fully sufficient.

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 only 40% (only accountId and profileId are documented), and the description compensates well: it explains postId's omission default, cursor's role as a nextCursor round-trip on specific platforms, and enumerates which platforms are valid. It says nothing about profileId or the accountId/profileId agreement rule, leaving the schema to carry those.

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?

States a specific verb ('List') and resource ('comments') scoped to one post on four named platforms, which cleanly separates it from list_posts, list_messages, reply_to_comment and delete_comment in the sibling set. An agent can identify the operation without opening the schema.

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?

Gives explicit conditional usage rules: 'Omit postId for the newest post' and 'pass nextCursor back as cursor for the next page'. It does not name an alternative tool or state when not to use this one (e.g. use list_posts for post-level data), so it stops short of full when/when-not/alternatives guidance.

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