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

Annotations already declare readOnly, idempotent, non-destructive, openWorld, so the safety profile is covered — and the description adds real behavioral context on top: the exact response envelope, the pagination discriminator (more.has_more / more.cursor) that differs from the 'after' of get_reddit_search and the 'cursor' of get_reddit_subreddit_search, nested replies with a 'more' object, and a concrete size signal (~21 KB for 19 top-level comments). The size and cross-tool paging distinction are exactly the details annotations cannot carry.

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 what is returned, then paging, then size, then routing to alternatives — a sensible information order with no filler sentences. The long flat field enumeration for comments is dense but each item is a genuine return-value fact; it is verbose rather than wasteful.

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?

For a read-only fetch with an output schema present, the description covers the non-obvious essentials: paging mechanics, relative payload size, and where to get the URL from. It would be a 5 with any note on rate limits/auth or on the trim flag, which is the one affordance an agent could use to control the 21 KB payload.

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 75%, so the baseline is 3; the description does add value by explaining what the cursor pages through ('more comments, or replies') and how the returned paging shape differs from sibling tools. However, the trim boolean and the undocumented string parameter 'trimmed' are never addressed, and trim is material because it changes the response size that the description otherwise quantifies.

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 and resource ('Returns one post and its discussion from a post URL') and then enumerates the exact fields returned for both the post and each comment, making the scope unmistakable. It is clearly distinguishable from get_reddit_search and get_reddit_subreddit, which it names as upstream discovery tools rather than competitors for this job.

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?

Explicitly routes the agent: 'To find posts worth opening, start from get_reddit_search or get_reddit_subreddit,' which tells the agent this tool is for opening a known post, not discovering one. It also tells the agent how to fetch more via the more.has_more / more.cursor pair. It stops short of stating when not to use it (e.g. bulk fetches) or prerequisites, so it is not a full 5.

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