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

Annotations cover read-only/open-world, but the description adds real operational detail beyond them: results cap at 100, there is no cursor, and the directory metadata updates infrequently so retrieved_on and subscribers are archive snapshots. That snapshot caveat is exactly the kind of subtlety an agent needs before treating subscriber counts as current.

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?

It is front-loaded with purpose, then parameter notes, then the result-cap constraint, then sibling routing, with no filler. The sort_by/sort enumeration is mildly redundant with the schema, so it is dense but not maximally economical.

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 an output schema present, return values need no explanation, and annotations carry the safety profile. Everything an agent needs to call it correctly, including the hard result cap, the absence of pagination, and the stale-snapshot semantics, is stated.

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 100%, so the baseline is 3, but the description adds meaning beyond the schema by framing subscriber filters as operating on archived snapshot values rather than live counts. The enumeration of sort_by and sort values does duplicate what the schema already states, keeping this below a 5.

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?

The first clause specifies a concrete verb (search), a precise resource (Arctic Shift's archived subreddit directory), and the discovery mechanism (name prefix) with optional filters. An agent can immediately tell this apart from reddit_subreddit_about or reddit_subreddit_posts without reading 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?

It explicitly routes the agent: use reddit_subreddit_about for a known community's feed-derived metadata, and reddit_subreddit_posts for current posts. That gives both a when-to-use-this (prefix discovery of unknown communities) and named alternatives with their own conditions.

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