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

Annotations cover the read-only/open-world profile, and the description adds genuinely non-obvious behavior: the surface-dependent shape (on `shreddit` subscribers, creation date and privacy come back null), the alternate weekly activity fields, and the 1-credit cost. Missing: nothing about rate limits, failures on private/banned subreddits, or caching behavior.

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?

Three dense sentences, front-loaded with the resource and its fields, then the caveat about `raw.via` and nulls, then cost. Every sentence carries information, though the field enumeration is a long clause that could be tightened.

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 return fields and the surface-dependent nulls, which is the right instinct. Gaps remain for a 2-parameter tool: `cache_max_age` is unexplained and there is no mention of behavior when a subreddit is private, banned, or nonexistent.

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 only 50%: `subreddit` is documented (name or full URL) but `cache_max_age` has no schema description and the tool description never mentions it either, so its units and effect are unknown. The description's only parameter-adjacent content is the credit cost. Below the high-coverage baseline because the uncovered parameter is left entirely unexplained.

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 the resource (a subreddit) and enumerates exactly which metadata it returns: title, description, icon, banner, subscribers, online-now, creation date, privacy status. That is far more specific than a tautology. It does not, however, distinguish itself from the sibling reddit_subreddit (subreddit posts) or reddit_search, so the agent must infer the boundary.

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?

Usage is implied by the field list – you call this when you need subreddit metadata rather than posts or search results – but no when-to-use/when-not-to-use statement or named alternative is given. With reddit_subreddit and reddit_search in the same family, an explicit routing rule would have been easy and valuable.

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