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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the tool's non-destructive, deterministic nature is known. The description adds valuable context beyond this: it returns JSON, works even when the image is partially distorted, and supports common image formats. It also discloses a per-call cost (10 points). These details enrich the behavioral profile without contradicting 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?

The description is compact, with three English/Korean sentences that cover the core function, output, robustness, and supported formats. The cost indicator is also included. There is minimal fluff, though the repetitive bilingual text slightly reduces elegance. It earns a strong 4.

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 single-parameter tool with no output schema, the description provides adequate completeness: it states the return type (JSON), robustness under image transformation, supported formats, and cost. The absence of an output schema is fine because the description defines the return type generically. No critical information for invoking the tool correctly is missing.

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?

The input schema provides 100% coverage of the image_url parameter, including allowed MIME types (image/png, image/jpeg, image/webp, image/bmp) and size limit (50MB). The description does not add any additional meaning about the parameter itself; it only refers to the image generically. With full schema coverage, a baseline of 3 is appropriate.

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 a specific verb ('Read') and resource ('the invisible watermark code embedded in an image'), and clarifies the output format (JSON). This clearly distinguishes it from sibling tools like set_watermark and draw_watermark_image, which are write operations. The purpose is unmistakable even without opening schemas.

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 clearly implies this tool is for retrieving watermarks, as opposed to embedding ones (set_watermark, draw_watermark_*). It provides practical context about robustness and supported formats ('PNG, JPEG 등 일반 이미지 포맷') and notes the cost ('[호출당 10포인트]'). However, it does not explicitly state when not to use it or mention alternatives, so it falls short of a 5 but is still clear on when it applies.

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