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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds meaningful behavioral context the annotations do not: the index is live/current and limited to newly submitted posts, which tells the agent results are recency-bound rather than a full corpus. It does not mention rate limits, result freshness lag, or pagination beyond the schema's 'after' field, keeping it short of a 5.

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 with zero filler: the first defines the operation and scope, the second routes to alternatives. The core capability is front-loaded before the disambiguation guidance.

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 and full annotations, the description need not explain return values, and it correctly covers scope, recency, and sibling routing. Minor gaps remain around default sort behavior and result freshness, but an agent has enough to call it correctly.

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 every parameter (q, sort, time, after, limit, subreddit) is already documented, establishing a baseline of 3. The description adds only marginal semantics for q — that matching applies to post titles or text rather than comments — which is useful but does not meaningfully extend the schema.

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 with scope: 'Search current Reddit communities site-wide for newly submitted posts whose titles or text match a keyword'. It also explicitly distinguishes itself from two named siblings (reddit_archive_posts_search, reddit_subreddit_posts), so an agent can select it 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?

Provides explicit when-to-use ('Use this live search for recent submissions') and when-to-use-alternatives with conditions: historical records → reddit_archive_posts_search, known community → reddit_subreddit_posts. Nothing is left to inference.

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