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

Annotations only cover readOnlyHint and openWorldHint, and the description adds real behavioral context beyond them: a 100-item cap and a per-call cost of $0.002 USDC via x402 payment. It still omits failure modes (unreachable site, no feed found) and whether truncation is silent.

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 tight sentences, front-loaded with the core purpose, followed by the cap and the price. Nothing is repeated from the schema or annotations and nothing is padding.

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?

With only two params, no output schema, and annotations covering safety, the description usefully lists return fields and the cost/limit constraints. Minor gaps remain around pagination, errors, and the x402 payment flow, but an agent has enough to invoke it 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 0%, so the description must carry parameter meaning. It does clarify that 'url' accepts either a feed URL or a website and that the item cap is 100 (relevant to 'limit'), but it gives no default, range, or behavior for 'limit' and no URL format guidance.

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 ('Read any RSS or Atom feed as clean JSON') and even enumerates the returned fields, plus a second mode ('give a website and we find its feed'). The resource is distinctive among siblings, but no sibling is named or contrasted, so it stops short of the 5 bar.

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?

Two usage contexts are given explicitly: pass a feed URL to read it, or pass a website to have the feed discovered. That is clear when-to-use guidance, but there are no exclusions or named alternatives (e.g. news, sitemap, serp) to route between when an agent is unsure.

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