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

Annotations already declare readOnlyHint=true, openWorldHint=true, and destructiveHint=false, so safety is covered structurally. The description adds genuinely useful context the annotations cannot carry: the returned fields, the fixed 20-posts-per-page pagination, the billing rate ($0.003 per request), and a surcharge for sentiment analysis. It omits failure modes, rate limits, and whether page 12 is a hard ceiling on result depth.

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 tight sentences, zero filler: purpose first, then return shape, then option surface, then the sibling hand-off and cost. Every sentence carries information an agent would otherwise have to infer.

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 usefully enumerates returned fields and adds pricing and pagination, so an agent knows what it gets and what it pays. The only real gap is get_sentiment, which modifies results and cost but is discussed only in the schema, and the description never notes search_reddit_users as a related alternative.

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 description coverage is 100%, so the schema already documents every parameter, including the enums for sort_by and posted_ago and the 1-12 page range. The description reinforces sort and time-window behavior but adds no syntax or format detail beyond the schema, and one naming drift ('newest' vs the schema's 'most_recent') risks mild confusion rather than adding clarity. Baseline 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 and resource ('Search Reddit posts by keyword') and explicitly carves out the comment-search case by naming search_reddit_comments, which is the closest sibling. An agent can distinguish it from search_reddit_comments and search_reddit_users without opening any 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 routing guidance for one alternative ('Use search_reddit_comments to search comment text') and describes the adjustable dimensions (sort order, time window). It stops short of full when/when-not coverage: nothing steers the agent away from this tool when it actually wants users, subreddits, or a non-Reddit source.

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