Url Images

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, destructiveHint. Description adds that it does not download images, does not execute JavaScript or bypass access controls, and caches results (fresh parameter). All consistent with annotations.

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?

Three sentences, no superfluous words, front-loaded with core purpose. Each sentence adds essential information.

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?

Given output schema exists (not shown but indicated), description covers all needed aspects: what it does, constraints, parameter guidance, and behavioral traits. No gaps.

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%, but description adds contextual value: explains cache reuse benefit and trade-off for 'fresh', and re-emphasizes that 'url' must be absolute public HTTP(S). Goes beyond mere schema comments.

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?

Clearly states 'List up to 100 image references without downloading images', a specific verb and resource. Differentiates from sibling tools (e.g., url_text, url_links) by focusing on images, and explicitly limits to public HTTP(S) resources.

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?

Provides clear context: use for public HTTP(S) URLs, no JS execution, no access control bypass. Offers guidance on the 'fresh' parameter (keep false for cache reuse, set true only when needed). Does not explicitly name alternatives, but the sibling list implies other tools for other purposes.

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