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

Annotations already cover safety (readOnly, non-destructive, idempotent, open world), and the description still adds genuinely new behavior: a cost model ('1 credit + 3 credits per post returned'), field names and an edge case ('score (can be negative)'), and the pagination contract with meta.nextCursor. That is exactly the kind of context annotations cannot express.

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 covering purpose, use cases, return shape, cost, and pagination, with the purpose and exclusion front-loaded. No sentence is redundant with the annotations or schema.

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?

Even without an output schema, the description enumerates the returned fields and the meta fields that drive paging and NSFW omission, discloses per-result pricing, and routes to the X equivalent. An agent has everything needed to call this correctly and interpret the response.

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 the baseline is 3; the description earns above that by tying limit to economics ('you pay per result' is in the schema, but '3 credits per post returned' here makes the tradeoff explicit) and by clarifying subreddit is 'without r/'. Sort/time/includeNsfw semantics are left entirely to the schema, which is acceptable given full coverage.

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 public Reddit posts by keyword') plus the scope modifier ('optionally inside one subreddit'). It also explicitly names the cross-platform sibling it is not ('Reddit only: search X separately with search_x'), so an agent can route without opening a 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 use cases ('opinions, complaints, recommendations and launch feedback') and an explicit exclusion with the alternative ('search X separately with search_x'), plus pagination guidance via meta.nextCursor. It does not, however, distinguish itself from the Reddit-side lookalikes (search_subreddit, get_subreddit_posts), which is the one routing ambiguity left open.

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