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

Annotations already cover safety (readOnly, idempotent, non-destructive), and the description layers on genuinely new behavior: the cost model ('1 credit + 3 credits per comment returned'), the flattened-plus-depth/parentId result shape, and the cursor contract. The per-comment billing detail is commercially material and appears nowhere in the structured fields.

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 short sentences, front-loaded with the core action and result shape, then sorting, then cost, then pagination. Every sentence carries a distinct, actionable fact with no filler.

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 does the necessary work of describing the return shape (flat list with depth and parentId) and the meta.nextCursor field. It omits which comment fields are returned (author, score, body) and how depth/limit interact with billing, minor gaps for a read tool whose safety profile is annotated.

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%, so the baseline is 3; the description still adds a selection rule for sort ('top' for most upvoted) and clarifies the resume protocol for cursor. It says nothing extra about depth, limit, comment, or context, all of which are left to the schema.

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?

Names a specific verb and resource ('Fetch the comment tree of a Reddit post') and pins down the output shape ('flat list, each with depth and parentId'). It doesn't differentiate from near neighbours like get_subreddit_comments or get_reddit_post, so an agent must infer the distinction from the required post id.

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 concrete operational guidance: 'Use sort=top for the most upvoted replies' and the exact pagination loop via meta.nextCursor. It never states when to prefer a sibling (get_subreddit_comments, search_reddit) or when not to use this tool, so it stops short of full routing guidance.

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