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

Annotations already cover the safety profile (readOnlyHint true, destructiveHint false, openWorldHint true), and the description goes well beyond them by disclosing the dedupe guarantee, cursor lifecycle, and the paid x402 model ($0.003 USDC per call, accepted chains, auto-pay clients, free sample). That payment/auth context is exactly the non-obvious behavior an agent needs before invoking.

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-loaded with the core behavior and then the call flow, params, and pricing in a logical order. It is dense and slightly crowded in the final sentences, but each element (cursor, price, sample) is actionable rather than filler.

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 3-param tool with no output schema, the description covers invocation flow, return semantics (new items only, cursor), and cost. It does not describe the item shape or error behavior, but the essential calling information is present.

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 67%, and the description supplies the meaning the schema omits for 'limit' ('max new items returned'), while cursor usage is explained in prose. The '1 to 50, default 20' detail largely repeats the schema's min/max/default, so it adds only modest value on top.

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 (RSS/Atom feed monitoring) plus the distinguishing behavior — 'returns only the items that are new since your last call, never the same item twice' — which separates it from a plain fetch such as the sibling rss_fetch. An agent can identify the tool's role without opening the schema.

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?

Explains the two-call flow clearly ('First call saves a baseline and returns a cursor; pass it on the next call') and enumerates supported feed types. It stops short of an explicit exclusion or naming of rss_fetch for one-off fetches, so it is clear context without full alternative routing.

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