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

With no annotations provided, the description carries the full burden of transparency. It discloses that a vision model is used and that the output is a textual description, which covers the core behavior. However, it does not detail output format, error scenarios, or limitations such as clipboard availability beyond what the schema mentions. It also does not explicitly confirm the operation is read-only, though '读取' implies it.

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 extremely concise, consisting of two short sentences that directly convey the function and usage context. It is front-loaded with the action and resource, and every word earns its place without any filler or repetition.

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 tool with only two parameters and no output schema, the description, combined with the detailed schema, provides sufficient context: what it does, when to use it, and what it returns ('返回文字描述'). It lacks some optional behavioral details like error handling, but these are not critical for such a straightforward read operation.

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 already provides comprehensive descriptions for both parameters, covering source types and the default prompt behavior, so the description adds little beyond what the schema states. The description's mention of source categories is redundant with the schema but consistent. Baseline of 3 is appropriate given the high schema coverage.

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 clearly states the tool's function with a specific verb ('读取图片') and resource ('image' from local file, URL, clipboard, recent screenshot), and further clarifies its purpose ('用于主模型无多模态输入能力时的识图'). This distinguishes it from potential alternative approaches and leaves no ambiguity about what it does.

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 explicitly states when to use the tool: when the main model lacks multimodal input capability. It also enumerates the types of image sources supported, providing practical context. However, it does not explicitly name alternative tools or exclusions, though the given context is sufficient for most use cases.

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