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

Annotations already cover safety (readOnlyHint=true, idempotentHint=true, destructiveHint=false), but the description adds useful non-schema context: the corpus size, the near-absence of captions, and the exact fields each result carries (image_url, coordinates, canonical page). It does not mention pagination defaults beyond the schema, but the added behavioral detail is substantial.

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 dense but front-loaded: corpus identity first, matching behavior second, return fields third, usage rule last. Every sentence carries information, with only minor overlap between the keyword-matching sentence and the caption caveat.

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?

There is no output schema, so the description must describe returns — and it does (image_url, coordinates, canonical IWAC page). Combined with corpus size, caption scarcity, and the no-arg listing behavior, an agent has everything needed to call this correctly.

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 89% schema description coverage the baseline is 3, but the description adds real value: it clarifies that keyword matches title/creator/subject/place/caption and warns that captions are almost never present, steering agents toward subject/place instead. That is meaningfully beyond the raw schema text, though it largely restates the schema's own field list.

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 names a specific verb+resource ('Search the IWAC photographs'), scopes the corpus (30 items: mosques, radio stations, schools, signage, street scenes) and describes the matching surface. It also distinguishes itself from the sibling alternatives (subject/place filters, semantic_search_images), so an agent can place it without opening a schema.

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?

It explicitly states the no-argument behavior ('Call with no arguments to list all') and gives a routing rule: prefer subject/place filters over keywords, or semantic_search_images when enabled. That is concrete when-to-use and when-to-prefer-an-alternative guidance.

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