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

Annotations already cover read-only safety, but the description adds materially: a per-record credit cost with a minimum of 2, a warning to keep page_size minimal, the fact that no score field exists, and the default-to-latest behavior when date is omitted. That is genuinely useful context beyond 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?

Every sentence earns its place: grain/semantics first, the no-score caveat, the cost constraint, then sibling routing. No filler, well front-loaded.

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?

An output schema exists so return-format explanation is unnecessary, and the description supplies the remaining decision-critical facts (cost, snapshot default, dataset limitation, alternatives). Nothing needed to call it correctly 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?

With 100% schema coverage the baseline is 3, but the description adds behavior the schema does not: omitting date selects the latest snapshot, and page_size has direct credit implications. These additions exceed the schema's field definitions.

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: searching stored daily snapshots of tracked subreddits' hot-feed order, with the record grain (one per subreddit, date, rank) made explicit. An agent can distinguish it from live-feed siblings without opening any 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?

Explicitly names three alternatives — reddit_search (live keyword), reddit_trends (current trends), reddit_subreddit_posts (single community) — and the conditions that select them over this stored-snapshot tool. Routing is unambiguous.

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