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

Annotations only cover read-only and open-world, so the description carries the real burden and does: 7 results per page, cursor consumption, 1-credit cost, `raw.posts` subreddit naming, `raw.via` surface tagging, and the important caveats that body text can be null and that scores/comment counts are null on the `atom` surface. These are non-obvious failure modes an agent would otherwise misread as missing data.

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 the core action, then layers pagination, result-shape, and cost in descending priority; every sentence conveys a distinct operational fact. It is densely packed with backticked field names, but nothing is filler.

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 7-parameter search tool with no output schema, the description covers result count per page, continuation, cost, null-field conditions, and which raw fields identify source and answering surface — enough to call and correctly interpret results. Only `cache_max_age` and `sort` semantics are left entirely to the schema.

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?

At 71% schema coverage the schema does most of the work, but the description adds real semantics: the cursor must come from `pagination.cursor` of a prior response, and `subreddit` narrows scope. One tension exists — the description says Reddit returns seven results a page while the `limit` schema claims 1-100 with default 25, which an agent may find confusing.

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 posts') plus the scope distinction of site-wide vs. one subreddit via the `subreddit` parameter. This makes it distinguishable from reddit_subreddit and reddit_post, though it never names those siblings explicitly to route the agent.

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?

Usage context is implied by 'site-wide or restricted to one subreddit', and pagination/cost guidance is given. But there is no explicit statement of when to use this instead of reddit_subreddit, reddit_userPosts, or reddit_postComments — the agent must infer the boundary from sibling names.

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