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

Annotations already cover the safety profile (readOnly, non-destructive, openWorld), yet the description goes well beyond them: page size (25), hard cap (~1,000 posts), explicit billing ($0.003/page), the posted_ago rejection rule, and the sentiment surcharge. This is exactly the cost/limit context an agent needs before invoking.

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?

Two dense sentences, front-loaded with the verb and inputs, then return fields, then pagination and cost. No sentence is padding; each carries a distinct constraint.

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 enumerates the returned fields (title, text, subreddit, date, score, upvote ratio, comment count, flair, links) and covers pagination, limits, and billing. Nothing an agent needs to call it correctly is missing.

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 all six parameters are already documented with defaults and enums. The description restates the key ones (sort order, posted_ago window and default) without adding syntax beyond the schema, so the baseline of 3 applies.

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+resource ('Get a Reddit user's submitted posts') and scopes it to posts rather than comments, which cleanly separates it from reddit_user_comments and reddit_user_profile. An agent can pick it 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 concrete operating rules: provide exactly one of username or url, and posted_ago only applies to top/controversial. However it never names the alternatives (e.g. reddit_user_comments for comments, search_reddit for discovery), so routing to siblings is left to inference.

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