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

The description adds behavioral context by stating that results are paginated and include image URLs in multiple sizes, photographer name, and attribution link. Since annotations already declare readOnlyHint=true and destructiveHint=false, the description complements rather than contradicts them, earning a 4.

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 a single, focused sentence that front-loads the purpose and then lists return values. It contains no fluff and is easy to parse, warranting a 5.

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?

Despite having only one parameter and an output schema noted, the description covers the tool's purpose, return values, and required input. Combined with annotations, this is sufficient for an agent to select and invoke the tool correctly, giving a 5.

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?

The input schema provides no description for the query parameter (0% coverage), so the description compensates by clarifying that 'query' is a keyword. It also notes that the keyword is required, adding meaning to the parameter. This is at a baseline level, thus a 4.

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 clearly states the tool searches Pexels photos by keyword and specifies the return content, making the core purpose unambiguous. It uses a specific verb 'Search' and resource 'Pexels photos.' However, it does not explicitly differentiate from sibling tools like photo_curated, so it earns a 4 rather than 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?

The description implies the use case (keyword-based photo search) but does not explicitly mention when to use this tool versus alternatives such as photo_curated or video_search. There are no exclusions or alternative recommendations, so the guidance is minimal, giving a 3.

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