search_images

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

With no annotations provided, the description carries the full burden and does so excellently. It discloses the critical CDN re-hosting behavior (raw Pexels URLs won't display), explains the default upload=true behavior, caching benefits, and the required environment variable. This is rich, non-obvious behavioral context.

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 concise and well-structured: it starts with the purpose, then a critical warning, explains the default behavior, provides usage guidance, and ends with the requirement. Every sentence earns its place and nothing is redundant.

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 no output schema, the description covers the essential aspects: purpose, key behavioral constraint (CDN whitelist), return value (cdn_url), and environment requirement. For a straightforward search tool with well-documented parameters, this is complete enough for an agent to invoke it 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?

Schema description coverage is 100%, so the baseline is 3. The description adds a little context around the upload parameter by explaining the CDN re-hosting and cdn_url, but the schema already describes each parameter well. No significant additional meaning is provided beyond the schema.

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 stock photos (Pexels) for a page/product.' It clearly identifies what the tool does and its intended use case, distinguishing it from sibling image tools like upload_images or read_image.

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 provides clear usage context: use this tool to fetch stock photos and use the returned cdn_url for image src/product images. It also notes the environment variable prerequisite. It doesn't explicitly exclude alternatives, but the context is sufficient for an agent to decide when to use this tool.

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