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

Beyond the readOnly/openWorld annotations, the description discloses a critical non-obvious behavior: it is pay-per-call via x402 USDC on Base, and the response returns a payment challenge if payment is absent. This is exactly the kind of cost/auth context an agent cannot infer from annotations. It stops short of covering failure modes for non-HTML or paid-response shape.

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 tight sentences with the core transformation front-loaded and the payment caveat second. Nothing is wasted, though the opening is clipped enough to read as a fragment rather than a full statement.

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 an output schema present, return values need not be described, and the payment flow is explained. For a single-parameter read tool with rich structured metadata, this is close to complete; only handling of non-HTML or failed extraction is unaddressed.

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 100% and there is only one parameter, so the schema already documents the URL. The description reinforces that it must be public and adds nothing about syntax, formatting, or edge cases, so the baseline 3 applies.

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 concrete transformation: a public URL becomes clean Markdown plus metadata, which is far more informative than the bare name/title 'extract'. It is unambiguous about input and output kind, though the phrasing is a noun fragment rather than an explicit verb statement, and there are no sibling tools in the same domain to distinguish against.

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?

'Any public URL' and the schema's 'must return HTML' imply when this is applicable, but there is no explicit guidance on when to use it versus other options or what inputs are out of scope beyond the HTML hint. Usage is only implied, not spelled out.

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