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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description adds genuinely non-obvious operational context: a $0.005 USDC per-successful-call charge via x402 on Solana, and a documented HTTPS alternative endpoint. It stops short of describing failure behavior (paywall rejection, non-HTML URLs), so it is not a 5.

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 front-loaded sentences: what it extracts, then who it is for, then price and transport details. Nothing is padded, though the raw endpoint URL is slightly operational clutter for an agent that already has the tool bound.

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 spends its budget enumerating the returned fields, which is what an agent needs to judge fit. The remaining gap is edge-case behavior (paywall failures, pages with no OG tags), minor for a single-parameter read-only extractor.

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?

One required parameter at 0% schema description coverage, so the schema contributes nothing beyond 'string'. The description partially compensates by qualifying the input as a 'public URL', which implies reachability/accessibility constraints, but gives no scheme, format, or invalid-input guidance.

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 ('Extract') and an enumerated set of resources (Open Graph, Twitter Card, title/description, canonical, icons, JSON-LD @types) from a public URL. That enumeration distinguishes it from nearby siblings like web_to_text, url_markdown, or readability_extract, which return page content rather than metadata tags.

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?

'Ideal for link unfurling agents' implies a use case but names no alternatives and no exclusions — an agent cannot tell from this text whether to reach for seo_audit, html_to_markdown, or url_links_extract instead when it wants a richer page audit. Usage is only implied.

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