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 the critical behaviors: the call costs money, the exact price and payment rail, and that no account or API key is required. It also notes the returned fields (points, comments, links). It omits payment mechanics, whether the charge recurs per call, and failure/refund behavior, keeping it below 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?

Very short and front-loaded, with the price-signaling word 'Paid' first so an agent sees the cost before anything else. The final sentence is a bare URL with no explanation of its role, which is slight waste, but overall there is little fat.

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 two-parameter, no-required-input feed tool with no output schema, the description covers topic, ordering, payment cost and rail, auth requirements, and the returned fields. The main remaining gap is response structure and pagination/refill behavior, which are minor for a simple listing endpoint.

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 both n and sort are already documented including defaults and the 1-30 range. The description restates the default sort ('newest first') and confirms sort=top, adding only marginal meaning beyond the schema. Baseline 3 is appropriate here.

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 implied by the name and a concrete resource: HN stories about 'open source', newest first or by top, returning points, comments and links. That clearly separates it from buy_hn_ai-agents, buy_hn_rust and the other topic feeds. It stops short of naming a sibling alternative explicitly, so a 4 rather than a 5.

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?

It conveys the conditions of use (paid, $0.25 USDC on Base, no account or API key), which is real context an agent needs. But it never says when to choose this topic feed over buy_hn (the general feed) or a neighboring topic, and gives no guidance on when not to call it. Usage selection is left to inference from the topic name.

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