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

Annotations only cover readOnlyHint and openWorldHint, so the description carries the rest and does add real context: all matches are returned per selector (not just the first) and each call costs $0.004 USDC via x402. It stops short of covering failure behavior, rate limits, or how rendering timeouts are handled.

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?

Three short sentences, each carrying distinct load: capability, return semantics, and cost. The capability statement is front-loaded and there is no 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?

With no output schema, the description correctly compensates by stating the return shape (every match per selector) and the paid x402 cost, which is essential for an agent to invoke it. Minor gaps remain around error/timeout behavior and whether the payment is automatic or requires a prior x402_check precondition.

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 50%: 'selectors' is documented as CSS selectors in the schema and only echoed in the description, while 'url' is undocumented in both places (scheme requirements, redirects, allowed hosts). The per-selector return semantics add modest meaning beyond the schema, so baseline 3 holds.

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?

Names a concrete verb and resource (scrape text and attributes from a rendered web page using CSS selectors) and the word 'rendered' signals it works on JS-rendered pages, which separates it from static fetchers. It never names a sibling such as crawl or extract, so the differentiation is implied rather than explicit.

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?

'Rendered web page' implies this is the right choice when the page requires JS execution, but there is no explicit when-to-use, when-not-to-use, or named alternative among the many siblings (crawl, extract, browser_act, html_tables). Usage must be inferred from a single adjective.

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