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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, which the description confirms. Beyond that, it discloses substantial behavior: the paid capability ($0.003 USDC via x402 v2), the never-settling behavior on non-feed targets, the two-phase handoff with explicit GET/POST endpoints, the 50-item limit, and the no-auth requirement. This adds rich context without contradicting 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?

Four sentences, each with a distinct job: price warning, parse behavior, error/never-settle behavior plus handoff mechanics, and auth requirement. The cost is front-loaded as the most critical fact, and no sentence is redundant. Dense but efficient, with every word earning 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?

The description covers cost, input scope, output size, feed type validation, error behavior (422 and never settle), the exact payment/result exchange mechanics, and auth. Since an output schema is present to document the return shape, nothing an agent needs to select and invoke this tool correctly is missing.

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% and the url parameter is documented with format uri, so the baseline is 3. The description adds value beyond the schema by restricting valid targets to feed types, emphasizing public reachability, clarifying single-URL usage ('one public feed URL'), and showing how the URL is passed in the handoff. This meaningfully strengthens the agent's understanding of acceptable values.

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 states a specific verb ('Parses'), a specific resource ('one public feed URL (RSS 2.0, Atom, or JSON Feed)'), and a concrete outcome ('normalized JSON with feed metadata and up to 50 items'). This clearly differentiates it from siblings like extract_page_markdown and extract_structured_data, which target arbitrary pages rather than feed formats.

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 defines the tool's scope precisely—only RSS 2.0, Atom, or JSON Feed URLs—and warns that 'non-feed targets return 422 and never settle', setting agent expectations. It does not explicitly name sibling alternatives or state when-not-to-use conditions, but the feed-only constraint is clear enough to guide selection.

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