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

Annotations only cover the safety profile (readOnly, openWorld, non-destructive). The description goes well beyond them: thread order with depth/parent ID, 50 comments per page, up to ~4,000 per thread, >10 pages can exceed a minute on large threads, and a concrete price of $0.003 per page. Cost, pagination, and performance limits are exactly the behavioral context an agent needs.

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-loads the core purpose, then packs return shape, sort options, pagination, performance, and billing into tight clauses. Every sentence carries information; 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?

With no output schema, the description carries the return-value burden and does so: it lists the returned fields (text, author, score, date, permalink) and the thread structure (order, depth, parent ID), plus pagination and cost. Nothing essential for correct invocation is missing.

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 all five parameters are already documented, including the sort enum and the url/post_id mutual-exclusion rule. The description restates the sort options and the 'exactly one' constraint but adds no syntax or format detail beyond the schema, matching the baseline 3.

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 the comments on a Reddit post, replies included.' An agent can tell this returns a comment thread rather than post metadata. It does not explicitly name the sibling it differs from (e.g. search_reddit_comments, reddit_user_comments), so it lands at 4 rather than 5.

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?

The only usage constraint is 'by URL or post ID (provide exactly one)', which is really a parameter rule repeated from the schema. There is no explicit when-to-use-this vs. search_reddit_comments or reddit_post_details guidance, leaving routing to inference.

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