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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds value beyond them: it discloses that results are visually matched rather than keyword-matched, that there is no quota, and that includeImages caps image returns at 4.

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 short clauses, front-loaded with what the tool returns, then the retrieval mode, then the one parameter worth explaining. The telegraphic style is dense but readable; nothing is wasted, though it is clipped enough that some intent must be inferred.

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?

Annotations cover the safety profile and there is no output schema to explain, so the remaining burden is modest. Still, for a 3-parameter tool with zero schema documentation, leaving screenDocId and limit undefined and the limit-vs-image-cap relationship unclear leaves the definition short of 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 0%, so the description carries the full burden, yet it only explains includeImages ('returns the top matches as images (max 4)'). screenDocId and limit are never described, and the interaction between limit (default 12, max 48) and the 4-image cap is left ambiguous.

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 states the resource (screens) and the retrieval criterion (visual similarity to a given screen), which is enough for an agent to know what it returns. It distinguishes itself from keyword search with 'Visual, not keyword', but never distinguishes itself from the sibling search_screens_by_image, which sounds like it covers adjacent ground.

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?

'Visual, not keyword' implies the usage context and 'no quota' hints the tool is safe to call liberally, but there is no explicit when-to-use or when-to-prefer-an-alternative statement. With a sibling named search_screens_by_image, the absence of routing guidance is a real gap.

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