页面截图

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

With no annotations, the description carries the full burden. It usefully discloses the non-obvious default that base64 payloads are suppressed because of size, which is the single most important behavior here. It does not state what is returned when returnBase64 is false (a reference, a saved file, a truncated payload?), nor any permission or side-effect considerations, so the disclosure is partial.

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?

Two short sentences, zero padding, and the critical default-and-override pair is front-loaded exactly where the agent needs it. Nothing is repeated that the schema already covers verbatim.

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 5-parameter tool with no annotations and no output schema, the description omits the return shape: an agent cannot tell what comes back when returnBase64 is false, which is the default path. The tool is simple enough that this is a moderate rather than fatal gap, but the default outcome is left undefined.

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%, so the baseline is 3. The description reinforces returnBase64 with a rationale ('图片数据默认不回传（体积大）') that the schema only states tersely, but it adds nothing for format, quality, fullPage, or maxBytes, which remain schema-only.

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+resource ('对当前页面截图' – screenshot the current page), which is unambiguous about what the tool produces. However, it never distinguishes itself from the many sibling tools in the capture/recording family (capture_start, capture_stop, capture_save), leaving the agent to infer how page_screenshot differs from them.

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?

It gives one concrete usage rule: image data is not returned by default, so set returnBase64=true when you actually need to see the image. That is real conditional guidance, but there is no when-to-use/when-not-to-use framing against alternatives or any precondition (e.g., a page must be loaded/selected first).

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