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

Annotations already declare readOnlyHint, openWorldHint, and destructiveHint. The description adds genuinely useful context beyond that: page size (25), the ~1,000-post ceiling, and explicit billing at $0.003 per page. It does not describe auth or rate-limit behavior, so not a full 5.

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?

A single dense paragraph that is well front-loaded: purpose first, then return fields, then pagination and cost. Every clause carries information, though the run-on structure could be broken into shorter sentences.

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 (title, text, author, score, upvote ratio, etc.) and covers cost and pagination limits. For a 7-parameter read tool with full schema coverage and read-only annotations, this is nearly complete.

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 all 7 parameters including enums and defaults. The description reinforces mutual exclusivity of subreddit/url and the posted_ago sort dependency but adds no syntax or format detail beyond the schema.

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: "Get a subreddit's posts by name or URL", and scopes it further with sort options and return fields. The subreddit scope inherently distinguishes it from siblings like reddit_user_posts and reddit_post_details.

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 parameter-level constraints ("provide exactly one" of name/URL) and notes that posted_ago applies only to top/controversial. However, it never states when to prefer this tool over search_reddit or reddit_user_posts, so usage is only implied.

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