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

Annotations already declare readOnlyHint=true, openWorldHint=true, destructiveHint=false, so the safety profile is covered. The description adds useful non-annotation context: exact billing ('Billed $0.003 per page') and the fact that sentiment adds a surcharge, plus what each result contains. That is real value beyond the 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?

Front-loaded with the core action, then the return payload, then the sibling redirect and price. Every sentence carries information, though the long return-field enumeration ('a link to the comment and a link for the parent post...') is dense enough to be slightly at odds with the conciseness goal.

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?

There is no output schema, so the description correctly steps in by enumerating returned fields (comment text, subreddit, author, date, IDs, links). Combined with the pricing note and the sibling redirect, an agent has enough to call it correctly; only sort/pages behavior is 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?

Schema description coverage is 100% and includes an enum and defaults, so the schema already carries parameter semantics; baseline 3 applies. The description restates the query and subreddit scoping but adds no syntax or format detail beyond the schema, and it does not mention the pages or sort_by options at all.

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+resource ('Search Reddit comments') plus the scoping modifier ('by keyword, optionally in one subreddit'), and explicitly routes the agent to the sibling tool for the other content type: 'Use search_reddit for posts.' An agent can distinguish this from reddit_post_comments and search_reddit 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?

Names one concrete alternative and the condition selecting it ('Use search_reddit for posts'), which is exactly the disambiguation an agent needs among the ~90 sibling tools. There is no explicit when-not guidance beyond that (e.g. versus reddit_user_comments or reddit_subreddit_details), so it falls short of a 5.

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