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

Annotations already declare readOnlyHint, destructiveHint=false, and openWorldHint=false, so safety is covered. The description adds real value beyond that by disclosing the return shape (each result has a block plus a preview) and the precondition that a startTime must be assigned before add_block — meaningful workflow context not in the annotations.

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?

Only two sentences, so nothing is bloated, but the phrasing is loose: 'for a project's picture' and 'its block' have unclear referents and force the reader to infer that 'block' is the returned media object.

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?

For a read-only search with no output schema, explaining the block/preview result shape and the startTime prerequisite is a solid foundation. It still leaves pagination behavior, result limits, and the meaning of the query and kind parameters unaddressed for a three-parameter tool.

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 0% across three parameters, so the description carries the full burden, and it largely omits them. The query string 'q' is never explained, the images/videos enum is only hinted at by 'photos or video clips', and the page parameter with its 1-50 range is not mentioned at all.

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 concrete verb+resource pair: find free stock photos or video clips. The media type ('photos or video clips') implicitly separates it from search_music and search_voices, though it never names them explicitly.

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?

Gives a useful downstream hint that results feed edit_project add_block once a startTime exists, which implies the tool is a sourcing step before editing. It offers no explicit when-to-use vs when-not guidance and does not mention the sibling search tools for music or voices when a project needs other assets.

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