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

Goes well beyond the annotations: discloses the exact price (0.001 USDC on Base via x402), that payment occurs only after buyer approval, and that nothing is charged on failure. The readOnlyHint=false is consistent with a tool that triggers a payment side effect, so there is no contradiction.

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?

Purpose and exclusions are front-loaded and every sentence carries information (limits, exclusions, price, refund policy). The dense nested parentheticals make it slightly harder to scan than it needs to be, but nothing is 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 still names what comes back (clean text, title, headings), plus size caps, cost, failure/refund behavior, and the sibling for the PDF case. Nothing an agent needs in order to invoke it 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 only 50% — url is documented in the schema and maxChars is not, though it carries default/min/max constraints. The description adds useful caps (1 MiB page, max 10000 characters) but does not explain maxChars truncation behavior or the minimum, so it only partially compensates for the coverage gap.

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 ('extract clean text, title and headings from a public HTML or plain-text page') plus the output shape and hard limits. It explicitly distinguishes itself from the sibling via_extract_page (which handles PDFs), so an agent can choose correctly without opening either 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?

Gives explicit when-not-to-use conditions (no PDF, OCR, JavaScript rendering or links) and names the alternative tool with its price for the excluded case. It also notes PDF URLs are refused before payment, so the agent knows failure happens before cost.

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