Type text

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

Annotations only say it is a non-read-only, non-idempotent, non-destructive write; the description adds substantial context beyond that: the ADBKeyBoard IME dependency for non-ASCII, the keyboard switch-and-restore side effect, and the fact that the response/log never contain the text itself. The account/device lockout warning is real operational risk information not present in structured fields.

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?

Purpose and the focus prerequisite are front-loaded, and the encoding path plus safety warning follow in a logical order. It is denser than strictly necessary and the password/PIN warning, while valuable, sits slightly apart from the core typing behavior.

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?

With no output schema, the description takes responsibility for the return value ('reports only the character count, never the text itself') and also covers the IME prerequisite and post-condition. An agent has everything needed to invoke it correctly or to know when it cannot.

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 both parameters are already documented. The description reinforces that only the length of 'text' is echoed back, but adds no syntax, encoding, or format detail beyond the schema. Baseline 3 applies when the schema does the heavy lifting.

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 ('Type text into the focused input field') and explicitly distinguishes itself from the sibling adb_key ('For single keys (ENTER, BACK) use adb_key'). An agent can route between the two without opening either 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?

Gives the precondition ('Focus the field first; on a TV box, DPAD_CENTER on the field opens the keyboard'), names the alternative tool for a different use case, and adds an explicit when-not with a stop condition ('Never retry a wrong password or PIN... Stop and ask the user').

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