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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds substantial behavioral context beyond that: it discloses performance characteristics ('Measured at 8 to 16 seconds and 8 to 26 KB, the slowest endpoint here'), the pagination mechanism (after token), and the full list of fields returned. No contradictions with annotations.

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?

The description is dense but front-loaded: the core purpose and paging mechanism appear first, followed by output details and parameter behavior, then performance and alternatives. Each sentence contributes information without redundancy. It's longer than minimal but justified by the tool's complexity.

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?

Given the output schema is provided, the description doesn't need to enumerate return types, but it still lists key fields. It covers scope (all public subreddits), pagination, sorting, timeframe, performance, and alternatives. An agent has everything needed to decide when and how to call this tool 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 coverage is 100%, so baseline is 3. The description adds meaning to sort ('accepts relevance, new, top and comment_count') and timeframe ('narrows the window'), and explains the after token's role in pagination. It does not explicitly describe trim, but the schema already documents it, and the description provides enough added value to warrant a 4.

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 description opens with a specific verb and resource: 'Searches every public subreddit for posts matching a query and returns posts plus an after token to page.' It clearly distinguishes itself from sibling tools by naming get_reddit_subreddit_search and get_reddit_post_comments, so an agent can immediately tell this is the global search endpoint.

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 states when to use alternatives: 'To stay inside one community use get_reddit_subreddit_search, which is faster and pages with cursor rather than after; to read one post's discussion use get_reddit_post_comments.' This gives direct routing guidance with clear conditions, leaving nothing to inference.

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