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

Annotations only declare readOnlyHint and a questionable openWorldHint=false, so the description carries most of the behavioral weight and does it well: it discloses the returned fields (image URL, size, alt text, photographer, credit line) and the licensing obligations that constrain downstream use. Minor gap: it never says what happens per provider or whether results are merged/deduplicated. Note the mild tension with openWorldHint=false, since the tool queries third-party public APIs, though these are two bounded, named providers rather than an open-ended web.

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?

Three sentences, front-loaded with what the tool does, then what it returns, then the licensing rules the agent must follow. The license sentences are longer than typical but earn their place because they constrain how returned images may be used.

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 usefully enumerates the returned fields and the credit-line obligation, and with 100% schema coverage the parameters need no further explanation. What remains thin is result behavior (per-provider vs merged results, empty-result handling), but for a three-parameter read tool this is largely sufficient.

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 query, limit (max 20, default 6) and orientation are already fully documented with examples. The description adds nothing about parameter behavior — notably that limit applies per provider, which the schema states but the prose does not reinforce.

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 free stock photos for the page or app the user is making') and names the exact upstream providers (Pexels and Pixabay), which separates it from the generic find_assets sibling.

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 gives clear context for when to use it (supplying imagery for a site/app being built) plus concrete usage constraints: credit the photographer, download Pixabay images rather than hotlinking, no reselling. It does not explicitly contrast with find_assets or state when not to use it, so it falls short of a 5.

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