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

Goes well beyond the annotations by disclosing that the call returns the app's new state with the next snapshotId (no extra snapshot needed), that a changed window aborts the action and returns the current state to retry from, that a sent action does not prove success, and that ui/process permission is required. The destructiveHint annotation is matched by the explicit 'replace the text' wording rather than contradicted.

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 the core action, then layers prerequisites, return semantics, and failure behavior. Dense and slightly telegraphic in places ('A sent action is not proof the task succeeded'), but nearly every sentence adds information an agent needs.

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 does the work of explaining the return value and the error-with-state recovery path, and it lists required permissions. The main gap is the undocumented elementId parameter, but overall the picture is complete enough to invoke correctly.

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 40% across five parameters. The description meaningfully constrains snapshotId to the latest app_snapshot and implies a UI element target, and deviceId/workSessionId carry their own schema descriptions, but elementId and the text length bound are left entirely to the schema.

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: replacing the text of a text field on the latest app_snapshot, with an explicit scope limit (never a password field). It is clearly distinguishable from siblings like app_press or app_select, though it does not explicitly contrast itself with the similarly named browser_type.

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 gives real operational context: the field must belong to the latest snapshot, apps that don't register typing as an edit require an explicit save, and ui/process permission is needed. It stops short of naming alternatives or stating exclusions beyond the password-field restriction.

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