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

Annotations already cover read-only/idempotent/open-world, but the description adds critical economics ('Costs 1 credit + 3 credits per comment returned') plus a non-obvious filtering rule: NSFW is judged by the comment's post, and omissions are surfaced in meta.omittedNsfw so an empty page isn't misread as a quiet community. These are behavioral traits no structured field conveys.

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?

Front-loaded with purpose, then alternatives, then cost and pagination — a sensible ordering. The framing sentence about busy communities is slightly wordy but earns its place by motivating the monitor alternative.

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 burden of explaining returns and does so: each comment carries its post (`linkTitle`, `linkPermalink`), and paging/omission state lives in `meta.nextCursor` and `meta.omittedNsfw`. An agent has everything needed to call it and interpret the response.

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 schema already documents all four parameters; the description reinforces the high-value ones — multi-community `+` joining, the includeNsfw default and its omission reporting, and the cursor's binding to other parameters. It adds workflow context rather than new field-level semantics, so it sits above the baseline but not at the top.

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 ('Read a community's newest comments') and pins the scope ('across every post', 'newest first'). It also distinguishes itself from the search siblings by stating that Reddit's search does not search comment text at all, which differentiates it from search_reddit/search_subreddit without opening a 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 an explicit use case ('the way to find mentions inside comments') and an explicit alternative with its selecting condition: for continuous watching, create a `subreddit_comments` monitor, which also filters by keyword. It also states when to call again (when meta.nextCursor is set) and the NSFW default.

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