List the images on a page

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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds genuinely new context: lazy-loaded images are included, and the call costs '1 credit', which is a cost disclosure annotations cannot express.

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 compact sentences front-load what is returned and follow with the use case, plus a terse cost note. Every element carries information, though the trailing '1 credit.' fragment is abrupt.

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 carries the return-value burden and does so by naming the fields returned (URL, format, dimensions, file size). Combined with complete parameter docs and existing annotations, an agent has enough to call it correctly; pagination/ordering behavior is the only notable omission.

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 all three parameters (url, limit, min_width) are already documented with meaning and defaults. The description adds no syntax or constraint detail beyond the schema; 'including lazy-loaded ones' is behavioral, not parameter-level. 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?

States a specific verb+resource ('List the images on a web page') and enumerates the returned fields (URL, format, dimensions, file size), which lets an agent distinguish it from extract_links, extract_metadata and screenshot by resource type. It never names a sibling explicitly, 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?

'Use it to find photos, logos or product images on a page' gives a concrete use context. There is no when-not guidance and no routing to alternatives such as extract_links when the agent actually wants hrefs rather than image assets.

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