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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, open-world), and the description adds real value on top: it discloses that results come from a web_search site:reddit.com passthrough and that results are cached for 2 days, which explains freshness and the force_refresh flag. It does not describe result volume, ranking, or whether snippets or full threads are returned.

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 the tool returns and for whom, then mechanism, then use cases, then query recipe, then caching — a sensible order with no filler sentences. The telegraphic "Cache 2 days" fragment is slightly terse but not 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?

No output schema exists, yet the description never says what a caller gets back (thread titles, URLs, snippets, how many). For a 4-parameter search tool with an out-of-domain ad_account_id parameter, one clause on return shape and on why the ad account is needed would close the remaining gaps.

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 most parameters are already documented, and the schema's keywords example ("vegan skincare hate") largely duplicates the description's query-construction guidance. The "Cache 2 days" line indirectly explains force_refresh, but nothing explains why a Meta ad_account_id is needed for a Reddit search — a genuinely confusing parameter left to the schema's terse note.

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?

"Reddit threads about a product or a pain, for customer language" plus "Search Reddit via web_search with site:reddit.com filter" names a specific verb, resource, and even the underlying mechanism. It is distinguishable from fetch_customer_reviews or fetch_ad_comments because the source (Reddit) and output (threads) are explicit, though it never explicitly contrasts itself with those siblings.

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 use cases (ICP pain point mining, customer language extraction, community dialect) and the exact query pattern to build (product keywords + signals like "hate", "alternative to"). It does not state when NOT to use it, e.g. when fetch_customer_reviews or search_meta_ad_library would be the better source, so the routing guidance is one-sided.

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