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

With no annotations, the description carries the behavioral burden. It discloses a non-obvious behavioral trait: the first call on a new site compiles a recipe and costs 300 credits, while later calls replay it for 1 credit per row. It does not mention authentication or error behavior, but for a read-style extraction tool the credit/caching model is the key extra context.

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?

Two sentences, front-loaded with the essential scope ('ONE page') and then the optional fields behavior. The examples are compact and every clause adds value; no 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?

An output schema exists, so the description does not need to document return values. It covers the key operational details: single-page scope, custom vs default schema, and the credit/recipe lifecycle. Its main completeness gap is that it does not explain how this tool relates to crawl_site/detect_site, but that is minor given the clear 'ONE page' scope.

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 0%, so the description must explain parameters. It does a good job on `fields`, giving concrete schema examples and explaining the null/default behavior. However, `js` is left unexplained and `url` is only implicit; the description partially compensates but does not cover all three parameters.

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 opens with a specific verb-resource pair ('Extract structured data') and scopes it to 'ONE page', immediately distinguishing it from site-wide siblings like crawl_site. It also explains the core customization of the tool (fields schema), so an agent can tell what the tool is for 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?

The 'ONE page' phrasing implies this is the single-page counterpart to crawl_site, and the fields instructions give practical how-to-use guidance. However, it never names alternatives or states when not to use the tool (e.g. 'use crawl_site for multiple pages'), leaving selection largely to inference.

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