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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint, so the safety profile is covered. The description adds genuine behavioral context beyond them: the output contract ('返回实际PNG图片', important since there is no output schema) and the no-op default ('默认保持原方向、比例与内容'), which tells the agent that omitting parameters yields the untouched image. It still omits failure behavior for unreadable or oversized images.

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 compact sentences that lead with input/output, then capabilities, then the default, then the source constraint — well ordered with no filler. The telegraphic final fragment '图片来源三选一' is efficient but borders on underspecified.

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 9-parameter tool with nesting and no output schema, the description covers the essential shape: what comes in, what comes out, and the no-transform default. It is nonetheless thin on the three mutually exclusive sources, error/limit behavior, and how the prepared image is meant to be consumed downstream, leaving open questions against a fairly complex schema.

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 67%, so the schema documents most parameters; the description only maps capability names to operations (EXIF/crop/rotation/perspective/scaling) without adding semantics such as what maxSide bounds or how the source parameters interact. With mid-to-high coverage and a genuinely detailed schema, baseline 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?

States concrete verbs and resource: reads PNG/JPEG and returns a real PNG image, then enumerates the supported transforms (EXIF orientation, crop, clockwise rotation, four-corner perspective, scaling). The purpose is unambiguous and clearly separable from the scene-building siblings, but the description never names or distinguishes itself from any sibling, and the title's '题目图片' framing is not carried into the description.

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?

'图片来源三选一' signals that exactly one of the three source inputs should be supplied, which is real usage guidance, and the default-preserving clause implies the tool is a pass-through unless transforms are requested. However, there is no explicit statement of when to reach for this tool (e.g., before passing an image to preview_scene) versus other approaches, and no when-not-to-use guidance.

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