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

Annotations already declare readOnlyHint=true and openWorldHint=true, covering the safety profile. The description adds that results are submissions matching the phrase, which is modest context, but it discloses nothing about pagination behavior, result counts, or the 'after' cursor's role beyond what the schema states.

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?

Two sentences, front-loaded with the core action and scope, with no filler. The second sentence about results and use case earns its place, though it borders on restating the first.

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-value explanation is unnecessary, and all parameters are documented in the schema. The description covers purpose and scope adequately for a six-parameter search tool, with only minor gaps around when to prefer scoped alternatives.

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 the schema already documents all six parameters including q, sort, time, after, limit, and subreddit. The description adds no parameter-level syntax, defaults, or format details, so the baseline 3 for full schema coverage is appropriate.

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 (Search) and resource (Reddit communities/posts) plus the matching target (titles and text) and the keyword-query mechanism. However, it does not differentiate itself from subreddit-scoped siblings like reddit_subreddit_posts in the sibling list, so an agent must infer the distinction from the 'site-wide' phrasing alone.

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?

'use this for site-wide topic discovery' implies the intended use case and hints that it is the broad/global variant. There is no explicit when-not guidance and no named alternative for scoped or subreddit-restricted searches, so usage is only implied rather than spelled out.

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