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

With annotations only covering readOnlyHint and openWorldHint, the description carries real behavioral weight: rate-limit handling via 503/Retry-After, a Redlib fallback path, and the promise that source.type=redlib preserves public fields and credit weights. These are non-obvious operational traits an agent needs before calling.

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?

Four tightly-packed sentences with no filler; the throttling and fallback details are front-loaded after the purpose. Slightly dense jargon (source.type, credit weights) but every sentence earns its place.

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?

For a 5-param read tool with an output schema, the description covers the failure modes and fallback behavior that the schema and annotations cannot. Missing only explicit guidance on pagination interaction with 'after' and the domains of competing sibling tools.

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 sort/time/after/limit/domain semantics are already fully documented in the schema. The description adds no additional parameter-level meaning, so the 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 submitted from a linked domain.' This distinguishes it from the named sibling reddit_user_posts, but leaves ambiguity against other reddit siblings such as reddit_search, reddit_subreddit_posts, and reddit_post that also return posts.

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 routes the agent away for one case ('Use reddit_user_posts to list Reddit user posts') and gives operational guidance for throttling (503 + Retry-After). It does not clarify when to prefer this over subreddit-based or search-based siblings, so the alternative mapping is partial.

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