screen_type

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

With no annotations provided, the description carries the full burden of behavior disclosure. It reveals important behavioral traits: the environment variable requirement and the clipboard fallback for non-ASCII characters. This goes beyond a simple 'types text' and gives the agent actionable details. It does not cover error cases or focus management, but for a simple input tool this is substantial.

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 two sentences, with the core purpose front-loaded in the first three characters. Every word earns its place: the prerequisite and behavioral split are both critical. No fluff 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?

Given the tool's simplicity (one parameter, no output schema), the description provides sufficient context for correct invocation: what it does, when it works (env var), and how it handles different text types. The only gap is lack of details about focus management or post-input behavior, but these are not essential for basic usage.

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 schema has 0% description coverage, so the description must compensate. It clearly explains the 'text' parameter's role: the text to input, with ASCII characters pressed directly and Chinese (or other non-ASCII) pasted via clipboard. This adds meaningful semantics beyond the bare schema, although it omits details like length limits or format requirements.

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: '键盘输入文本' (keyboard input text), specifying the verb (input) and resource (text). It also distinguishes from sibling tools like screen_click or screen_scroll by focusing on text entry, and the special ASCII vs clipboard behavior further differentiates it from screen_key.

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 provides an explicit prerequisite: VISION_ALLOW_SCREEN_CONTROL=1, indicating when the tool can be used. It also explains the two input methods (ASCII direct, Chinese via clipboard), which implies when each mode applies. However, it does not explicitly name alternative tools or exclusions, so it lacks a direct 'use this instead of X' comparison.

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