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

With no annotations, the description carries the full burden and does disclose genuinely useful behavior: the 100-post cap, 20 default, per-10-posts billing, and that failed/empty calls are free. It omits auth requirements, rate limits, and whether pagination is stable, so it is helpful but incomplete for a zero-annotation tool.

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?

Three short sentences, front-loaded with purpose, then result volume, then cost model. No filler, and each sentence adds decision-relevant information (source mode, size cap, billing behavior).

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 seven-parameter, zero-required listing tool with no output schema and no annotations, the description covers volume and cost but leaves auth, rate limits, and pagination behavior unaddressed. It is adequate but not complete.

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 seven parameters, including defaults and formats like 'without the u/ prefix'. The description repeats the 20/100 limits but adds no semantics beyond the schema, 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 ('List posts') and clarifies the two source modes (subreddit or user), so an agent knows what it returns. It does not name or distinguish itself from the siblings reddit_search or reddit_read, so routing among the trio still requires inference.

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?

The description implies when to use it (listing a feed for a community or user) and the schema notes that username and community are alternatives to each other. However, there is no explicit guidance on when to prefer this over reddit_search or reddit_read, and no prerequisites are stated.

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