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

Beyond the read-only/idempotent annotations, the description reveals that captions are almost never present, that results include image_url, coordinates, and a canonical page, and that calling with no arguments lists all items. These are non-obvious behavioral traits that affect invocation and interpretation of results.

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?

The description is four sentences, tightly packed with useful information: collection size, matching behavior, result fields, alternative tools, and usage tips. No filler or repetition; the structure front-loads the core purpose before adding nuance.

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's enumeration of result fields (image_url, coordinates, page) is essential and provided. The 30-item scope, no-argument listing, and mention of semantic_search_images cover typical agent questions. The description is complete for a search tool of this complexity.

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 coverage is high (89%), so baseline is 3. The description adds value by explaining that keyword searches rarely match captions, that subject/place filters are preferable, and that these filters are 'pipe-aware' (though that detail is in the schema). It compensates for the few undocumented parameters by giving selection guidance rather than re-listing parameter syntax.

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 opens with a specific verb and resource: 'Search the IWAC photographs', and clearly defines the collection scope (30 items, content types). It distinguishes itself from siblings by focusing on photographs and even references semantic_search_images as an alternative, while the no-arguments listing behavior further clarifies its purpose.

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?

Explicit guidance is provided: captions are rare, so users should prefer subject/place filters over keywords, and semantic_search_images is named as an alternative. It also explains how to list all items, which covers the common 'no filter' use case. This directly helps an agent choose between this tool and siblings.

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