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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds genuinely new behavioral context — throttling semantics (503 + Retry-After), automatic Redlib fallback, and that public fields/credit weights are preserved across the fallback. It stops short of describing field shape or normalization details, so not 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?

Front-loaded with the core purpose and operational caveats, and every sentence carries information. Slightly cluttered by the inline 'subreddits:' fragment, which reads as schema repetition wedged into the prose, but it is not egregiously long.

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 shape needn't be explained. The description covers selection, throttling behavior, and fallback semantics for a read-only open-world fetch tool. Remaining gaps (auth requirements, normalization rules) are minor given annotations and the output schema.

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 five parameters including sort, time, after, limit, and subreddits. The description merely restates the subreddits constraint ('required, maximum 10') that already appears in the schema, adding no syntax or semantic detail. Baseline 3 applies.

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 ('Returns normalized public posts from a combined multi-subreddit feed') and explicitly differentiates from the closest sibling by naming reddit_subreddit_posts as the single-subreddit alternative. An agent can select it without opening either 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?

Names the alternative (reddit_subreddit_posts) and the condition that selects it, plus operational guidance: retry on 503 after the Retry-After seconds, and the Redlib fallback applies on native-source failure. Explicit when-to-use and what-to-do guidance is present.

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