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

Annotations already declare readOnlyHint=true, openWorldHint=true and destructiveHint=false, so the safety profile is covered. The description adds behavioral context beyond that — it discloses a "Fast HTML streaming parser" implementation trait — but omits error behavior for non-HTML/unreachable pages, caching, or rate limits.

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, which is good, but "title, description, image" is effectively stated twice (opening sentence and the field enumeration), and "Link preview" as a standalone fragment adds little. Wasteful repetition keeps it from scoring higher.

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?

There is no output schema, so the description usefully enumerates the returned fields (title, image, favicon, site name, language, canonical URL, author, publish time, Twitter card, JSON-LD). Combined with annotations covering safety, an agent has enough to call and interpret the tool, though error/edge behavior 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%, so the schema already documents both url and jsonld; baseline is 3. The description's mention of "optional JSON-LD" corroborates the jsonld parameter but adds no syntax or format detail 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?

The opening sentence gives a specific resource and what is extracted (title, description, image of a web page), and the field list clarifies the scope. It does not name or distinguish itself from web-metadata siblings like check_url_status, expand_short_url, or extract_links, so it stops short of a 5.

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?

"Everything you need to build link previews" implies the use case (generating link previews / scraping page metadata), but there is no explicit when-to-use vs. alternatives guidance and no exclusions. Usage is only inferred from the field list.

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