Image Search

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

Annotations already declare readOnly, idempotent, non-destructive, open-world behavior, so the safety profile is covered. The description adds genuinely new context: that small thumbnails can be inlined as base64 data URIs, which affects response size and payload handling — a behavior not visible in annotations or the schema's short parameter note.

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 tight sentences with the core action front-loaded and no filler. The second sentence largely restates the includeThumbnails parameter already documented in the schema, which is mild redundancy but not wasteful.

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 10 fully documented parameters and an output schema present, the description needn't explain return values, and pagination/limits are covered in the schema. The only real gap is the absence of guidance on choosing between this and the sibling search tools.

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%, including enums, defaults, ranges, and the engine auto-fallback note, so the schema carries the semantic load. The description adds nothing beyond what the schema already documents about parameters, making the baseline 3 appropriate.

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 ('Search images') and the scope ('across engines that support it'), which distinguishes it from the generic web_search sibling. It stops short of explicitly naming web_search or list_engines as the alternative, so differentiation is implied rather than stated.

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?

No explicit when-to-use/when-not guidance and no mention of the obvious alternatives (web_search for text results, list_engines for discovering image-capable engines). The phrase 'engines that support it' hints that some engines are image-incapable, but the agent must infer when to prefer this tool.

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