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

Annotations already declare readOnlyHint and openWorldHint, but the description adds real operational context beyond them: robots.txt compliance, refusal of private addresses, no JS rendering, per-page billing, and that failed pages are reported with a reason and not charged. This meaningfully reduces invocation risk.

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 that are front-loaded with the most important content (what data is returned) followed by constraints and billing behavior. Dense but every clause carries information; 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?

For a read-only tool with no output schema, the description enumerates returned fields, states failure/billing behavior, and lists access constraints (robots.txt, no private addresses, no JS). The main gap is sibling differentiation against url_to_markdown, which would make the definition fully self-sufficient.

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%, so both parameters (url and urls) are already documented, including the 'Use this or urls' guidance and the 20-item cap. The description only restates 'one or many public URLs' and adds the 'public' constraint, adding little beyond the schema.

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 resource (link-preview metadata for public URLs) and enumerates the returned fields (title, description, canonical URL, OG/Twitter, favicon, language, hreflang, feeds, JSON-LD types), so the agent knows exactly what it gets. However, it never names or contrasts with the obvious sibling url_to_markdown, so differentiation is left to inference.

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?

Usage is only implied through the field list and the 'no JavaScript rendering' caveat. There is no explicit when-to-use statement and no routing to alternatives such as url_to_markdown, so an agent must infer the choice rather than being told.

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