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

Annotations already declare readOnly/openWorld/idempotent, so the safety profile is covered. The description adds genuinely useful behavior beyond that: robots.txt is respected, and the paid model is disclosed ($0.002 USDC via x402 or prepaid credits, free trial) — payment/auth context an agent needs before invoking.

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?

Front-loaded with the core purpose and return contents, then use cases, then the robots.txt and pricing caveats. Every clause carries information; nothing is padding.

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?

An output schema exists, so return values need not be explained. The description covers what it returns, who it's for, compliance behavior, and cost — everything an agent needs to decide and invoke correctly.

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% for the single 'url' parameter, so the schema fully documents it. The description adds no syntax, format, or constraint detail beyond what the schema already provides, so 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 names the resource (a web page's metadata) and enumerates the exact return surface — title, description, canonical URL, OpenGraph/Twitter tags, icons, feeds, JSON-LD types — so an agent can distinguish it from siblings like extract, markdown, feed, or sitemap without opening the 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?

It gives concrete use cases ('For link previews, SEO checks and crawlers'), which tells the agent when this tool is appropriate. It stops short of naming alternative tools or stating exclusions (e.g., when to use extract or markdown instead).

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