search_images

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

Despite readOnlyHint=true already covering the safety profile, the description discloses substantial behavior: default re-hosting on the WebCake CDN, caching so repeats are free, the domain-whitelist rendering constraint, and the PEXELS_API_KEY environment requirement. This is exactly the auth/side-effect context annotations cannot express.

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?

Front-loaded with the purpose, then the critical rendering constraint, then defaults and the auth prerequisite. Dense but no filler; the uppercase IMPORTANT is slightly heavy-handed but serves a warning function.

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 carries the return-value burden well by naming cdn_url as the ready-to-use output and explaining caching. Combined with the auth prerequisite and the four documented params, an agent has everything needed to call 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 coverage is 100%, so the baseline is 3, but the description adds real meaning by tying the `upload` parameter to its consequence (re-hosting, ability to display) and introducing the returned `cdn_url` concept. It enriches the schema rather than repeating it.

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 and resource ('Search stock photos (Pexels)') with the target context ('for a page/product'). It is clearly distinguishable from the nearest sibling, upload_images, which handles the user's own uploads rather than external stock search.

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?

Provides strong context: the CDN whitelisting constraint tells the agent when this tool matters and warns that raw Pexels URLs won't render. It implies usage for page/product imagery but never names an explicit alternative (e.g. upload_images) or a when-not-to-use case.

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