screenshot_annotated

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

With no annotations, the description carries the full burden and does disclose a real behavioral constraint: secure layers / DRM can produce a blank image or a refusal. It also documents that annotation is on by default and that optional disk saving exists. Missing detail on whether the image bytes or a path is returned, which matters given there is no output schema.

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?

Front-loaded with purpose, then limitations, then the default/annotation workflow, then the routing note. The exclamation marks and mixed brackets are slightly noisy but every sentence carries distinct information.

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 3-parameter read tool with no output schema, the description covers the key gaps: DRM failure modes, the default annotation behavior, and the downstream action. Only the return shape (image payload vs. saved path) is left implicit.

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 coverage is 100%, so baseline is 3, but the description adds meaning the schema does not: it explains why `annotate_elements=True` matters (indices feed directly into `tap_element`) rather than just restating the flag. `max_width` and `save_path` are left to the schema, which is adequate.

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 a specific verb and resource ('获取手机屏幕截图') and immediately adds the distinguishing capability: the Set-of-Mark `[#0]`, `[#1]` overlays. It also names `get_ui_tree` as the different sibling, so an agent can tell the two apart without opening a schema.

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?

Explicit routing: prefer `get_ui_tree` for daily operations, use this only for Canvas / map rendering / games / visual verification. Both the when and the when-not are stated, plus the follow-up action `tap_element(index=编号)`.

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