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

Annotations already declare readOnlyHint=true and openWorldHint=true. The description adds valuable behavioral details beyond that: the pay-per-call model (USDC/USDT on Base via x402), the 3-free-calls-per-wallet rule, and the common-path fallback behavior. It does not mention rate limits or cancellation/reversibility, but the added cost and fallback disclosures go beyond the annotations.

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?

The description is exactly two sentences: the first front-loads the purpose and method, the second conveys payment terms. No filler or redundancy. 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?

Given the tool's simplicity, the description covers the core discovery action, fallback behavior, and payment requirements. An output schema exists, so return values need not be described. It does not address edge cases like what happens when no feed is found, but that is likely covered by the output schema and is a minor gap for a tool of this complexity.

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 fully documents all parameters. The description's mention of the fallback path gives behavioral context for the 'url' parameter but does not add meaning beyond the schema's parameter descriptions. Baseline 3 is appropriate.

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?

The description clearly states the tool's function with a specific action ('Find') and resource ('RSS/Atom feed URLs for a website'), and it explains the method (HTML link tags with a common-path fallback). This distinguishes it from sibling tools like rss_feed, which likely handles feed retrieval rather than discovery.

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 the tool (when you need to locate feed URLs) and provides payment/free-tier context, but it does not explicitly name alternatives or state when not to use it. No exclusions are given, but the usage context is reasonably clear.

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