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

Discloses limits (50 items, 2 MB), error behavior (non-feed pages return 422 and are uncharged), leniency with real-world feeds, and pricing/billing semantics (first 25 free, failed calls free). Critically, it pre-empts the surprising readOnlyHint=false annotation by explaining 'each call is charged,' turning a potentially confusing annotation into understandable behavior.

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?

Front-loads the core capability and return shape, then constraints, then usage, then pricing. Dense but each sentence carries information; only the mid-sentence pricing/billing clause mildly interrupts the flow.

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 no output schema, the description fully compensates by enumerating returned fields and formats, plus error and billing behavior. An agent has enough to call it correctly without inspecting anything else.

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 the schema already documents both params and the baseline is 3. The description adds value beyond it: a worked example (limit=10), the effective cap ('Up to 50 items'), and output-format semantics (ISO 8601 dates, short plain-text summary) that clarify what limit and url actually yield.

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+resource ('Read a public RSS 2.0, RSS 1.0 or Atom feed') and enumerates exactly what is returned (title, link, description, newest items with title/link/date/summary/author/id). This cleanly separates it from generic siblings like extract, extract_rendered and url_meta.

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?

Gives clear routing context: 'Use to follow news, blogs, release notes or podcasts without scraping pages,' which implicitly steers agents away from the scraping siblings. A concrete example (url, limit) is provided, though no sibling is named as an explicit alternative in the way the strongest definitions do.

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