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

The description discloses a critical behavioral trait not obvious from the schema: 'The search results do NOT include a download link.' This is a significant gotcha that prevents misuse. However, since no annotations are provided, the description carries the full burden; it does not mention other potential behaviors like pagination or rate limits, though the schema covers the page parameter.

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 fairly concise with only three sentences. However, the first two sentences are somewhat redundant (both mention searching/retrieving videos). The [CRITICAL] marker is useful and front-loaded enough, but the repetition prevents a perfect score.

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?

Given the tool's moderate complexity (4 params, no output schema), the description covers the essential use case, return metadata, and the critical follow-up requirement. It could be more explicit about the response structure (e.g., presence of the 'id' field) but it's implied. No output schema exists, so this is reasonably complete.

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% (all four parameters: query, page, size, orientation have descriptions). The description adds no additional parameter semantics beyond the schema, so the baseline score of 3 applies.

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 a specific verb and resource: 'Search for stock videos on Pexels' and 'Retrieves a list of high-quality stock videos matching a given query.' It also differentiates from the sibling tool 'get_media_detail' by explicitly noting that the download link is obtained through that tool, not this one.

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 explicit guidance on when to use this tool vs an alternative: 'You must pass the id of the chosen video to the get_media_detail tool to retrieve the actual download_link.' This clearly directs the agent to use get_media_detail when a download link is needed, establishing the proper workflow.

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