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

Annotations already convey the tool is read-only and open-world, but the description adds a large amount of behavioral transparency beyond that: credit costs per page and per cursor call, freshness cache behavior with fallback refunds, trial-key limitations on realtime, upstream per-query result-depth capping (a few hundred), and the absence of a server-side time window on comment search. This is exactly what an agent needs to predict behavior beyond 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?

The description is long but information-dense. Every clause earns its place: the result cap, credit costs, sort/range constraints, freshness behavior, cursor pagination, and sibling routing are all necessary for correct call construction. It avoids redundant phrasing and leads with the core purpose before diving into per-type and pricing nuance.

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?

This is a high-complexity tool (7 params, 4 enums, cost model, pagination, cache modes, type-specific behavior) with an output schema, yet the description covers all the non-obvious interactions, including trial-key limitations and polling guidance for comment search. The only missing details (full output fields) are already covered by the output schema, so nothing an agent needs is omitted.

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?

Despite 100% schema coverage, the description adds meaningful semantics: it explains the semantic purpose of `type=comments` ('what people actually say about a product...'), the allowed sort values per type, that range applies only to posts, and that cursor pages are new calls costing credits profit. It also warns that sort/range misuse is rejected with INVALID_INPUT. This goes far beyond the baseline schema-only value.

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?

The description opens with a clear verb+resource ('Search all of Reddit by keywords') and immediately distinguishes target types (`type` picks posts, comments, subreddits, users). It also names sibling tools for adjacent tasks (reddit_get_post, reddit_get_subreddit_posts, x_search), so an agent can unambiguously tell this from cousins.

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 tells when to prefer this tool and when not to: use `reddit_get_post` for full post bodies/threads, `reddit_get_subreddit_posts` for a community's feed, and `x_search` for high-volume recency sweeps on X. It also clarifies the unique value of comment search, making alternative-selection logic executable.

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