android_type

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

With no annotations provided, the description carries the full burden and does disclose key behaviors: ASCII-only limitation, optional pre-tap via ref, ENTER submission, screenshot return, and device defaulting. It could add what happens with unfocused fields or invalid refs, but the disclosed constraints are sufficient for safe invocation.

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 tightly structured: a one-sentence behavioral summary, a critical limitation, then a bullet-style arg list. Every line adds necessary information; there is no filler or redundant restatement of schema fields.

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 6-parameter tool with no annotations and no output schema, the description covers the essential selection and invocation context: what it does, the ASCII constraint, all parameter meanings, and screenshot behavior. It does not document error cases or the exact return payload beyond the screenshot, but it is largely complete for practical agent use.

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 0%, so the description must compensate, and it does: every parameter (text, ref, device, submit, screenshot, scale) receives a concise semantic explanation beyond its name/type. It clarifies defaults, side effects, and the meaning of scale as long-edge pixels, which is high-value guidance.

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 opens with a specific verb and resource: 'Type text into the focused field, optionally tapping a field first.' This clearly distinguishes the tool from siblings like android_tap (taps only) and android_key (sends key events), making its purpose unambiguous.

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 clearly states the tool is for typing text into a focused field and that a ref can optionally be tapped first to focus it. It does not explicitly name alternatives or when not to use it, but the usage context is clear and actionable. The ASCII-only note also helps the agent avoid sending unsupported input.

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