type_text

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

With no annotations, the description carries the full burden and does substantial work: it discloses destructive default behavior (replacement of existing value), the append escape hatch, that submit fires onSubmitEditing, and that a new screenshot is returned. It stops short of stating whether the field must be visible/on-screen to type, what happens if the target isn't found, or whether focus/scroll is adjusted first.

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?

Three tight sentences, front-loaded with the action and its default behavior, then location options, then return value. Every clause carries information an agent would otherwise have to guess.

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 six-parameter mutation tool with no annotations and no output schema, the description covers the risky parts (replacement, append, submit) and location strategies. Remaining gaps are mainly failure modes and coordinate semantics, which are secondary to selecting and calling the tool.

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 only 17%, so the description must compensate, and it largely does: it explains target as a testID/placeholder/accessibilityLabel/current-value selector, explains append's effect on replacement, and (via schema) submit. The x/y pair is left as bare coordinates with no unit, precedence, or behavior when both target and x/y are supplied.

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 ("Types text into a TextInput") and immediately states the default behavior (value replaced unless append=true). It is clearly distinguishable from siblings like click_screen and press_key, though it never names an alternative explicitly.

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 states the testing context ("so forms and validation can be tested") and gives concrete field-location strategies: target attributes, x/y coordinates, or omitting both for the focused field. What is missing is any exclusion or precedence rule (e.g., when to use target vs. x/y, or when to reach for use_target/click_screen instead).

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