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

Annotations already mark the tool as read-only, so the safety profile is covered. The description adds useful context about per-call cost and typical application areas, but it does not disclose the similarity score scale, failure behavior, or limitations beyond the schema-provided constraints.

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 compact and front-loaded with the core action. The English and Korean portions repeat the same information, which is mildly redundant, but the use-case and cost notes earn their place and the overall length is appropriate.

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 simple two-parameter read-only tool with a richly documented schema, the description provides enough to invoke it correctly: what it does, what it returns, when to use it, and its cost. The lack of an output schema leaves the exact score range ambiguous, but this does not block correct invocation.

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%, with both parameters fully documented for URL format, MIME types, and size limits. The description only restates the conceptual roles of the two images ('base image' and 'comparison image') without adding meaning beyond the schema.

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 uses a specific verb and resource: 'Compare a base image with another image and return a similarity score.' It also names concrete use cases—original verification and duplicate detection—which clearly distinguishes it from image editing, generation, and detection siblings.

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 gives clear usage context by stating the tool is for '원본 검증, 중복 이미지 탐지 등' (original verification, duplicate image detection, etc.). It does not explicitly name alternatives or when-not-to-use conditions, but the use cases provide enough guidance for selection.

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