Link preview

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds the output field list, which is genuinely useful given no output schema, but says nothing about failure modes for non-HTML resources, redirects, or fetch timeouts.

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?

A single front-loaded sentence with the action first and the return payload after a colon. No filler, though the field enumeration is slightly long relative to the one-parameter surface.

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 simple one-parameter read tool with no output schema, the enumerated return fields make the description self-sufficient about results. The only real omission is guidance on unrealistic URLs or missing preview data.

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 and schema coverage is 100%, with the schema itself noting "http(s) URL to preview". The description repeats "for a URL" but adds no constraints or format detail beyond the schema, 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 states a specific verb and resource ("Get a link preview for a URL") and enumerates the returned fields, so the agent knows exactly what it produces. It does not differentiate itself from siblings like fetch_url_as_markdown or generate_og_image, which keeps it from 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?

There is no statement of when to use this versus alternatives, even though fetch_url_as_markdown and generate_og_image occupy adjacent territory. The agent must infer that this is the metadata-extraction option rather than full-page content.

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