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

Discloses concrete behavior beyond the annotations: 512 KB read cap, no JavaScript execution, and a $0.001 USDC-on-Base cost via x402. These are exactly the operational facts an agent needs. The description reads as a pure read op while readOnlyHint=false, but the per-call payment gives a plausible rationale for the non-read-only flag, so this is tension rather than a hard 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?

Three well-ordered sentences: capability and returned fields first, constraints second, use cases and cost last. The field enumeration is long but earns its place given there is no output schema; only minor trimming is possible.

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 compensates by listing the returned metadata fields. Combined with the size cap, no-JS guarantee, and payment cost, an agent has everything needed to decide whether and how to call it.

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?

Only one parameter with 100% schema coverage, so the schema already documents the 'absolute public http(s) URL' constraint. The description reinforces 'public web page' but adds no new syntax or format detail beyond the schema baseline.

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+resource (fetch a page's head and return link-preview metadata) and enumerates exactly which fields come back. It is clearly distinguishable from siblings like screenshot, extract_rendered and html_to-text because it declares it reads only the head and never runs JavaScript.

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?

Explicitly names the intended use cases: build link previews, label citations, or check how a URL will unfurl before sharing. It does not name an alternative sibling or state when not to use it, so it stops short of a 5, but the context is unambiguous.

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