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

Discloses limit of 100 references, no-download behavior, no JS execution, and caching policy; all consistent with annotations (readOnlyHint, idempotentHint) and adds useful context beyond them.

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, each earning its place: first states core purpose, second adds usage restrictions and parameter guidance. No wasted words.

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?

Fully covers purpose, usage, parameter behavior, and constraints for a simple tool; no output schema needed per rules, and all key aspects are addressed.

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?

With 100% schema coverage, description adds value by providing concrete caching advice ('fresh=false to allow cache reuse') and confirming URL must be absolute public HTTP(S) URL, complementing the schema's pattern and examples.

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 clearly states it lists image references (up to 100) without downloading them, distinguishing it from other URL inspection tools like web.url.links or web.url.extract.

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?

Explicitly restricts usage to public HTTP(S) resources, states it does not execute JavaScript or bypass access controls, and provides guidance on caching behavior with fresh parameter.

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