Check if a UI element matching the specified selector exists on the Android screen. Provide at least one selector field to verify presence.
Check whether an element matching the selector currently exists on screen. Provide at least one selector field.
| Name | Required | Description | Default |
|---|---|---|---|
| text | No | ||
| index | No | ||
| description | No | ||
| resource_id | No | ||
| text_contains | No |
| Name | Required | Description | Default |
|---|---|---|---|
| result | Yes |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. 'Check whether' and 'currently exists' indicate a read-only, immediate operation, but it does not disclose what happens when no match is found, whether it only considers visible elements, or any error behavior. It is minimally transparent but not comprehensive.
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 short sentences with no unnecessary words. The functional purpose is front-loaded, and the required selector-field constraint is stated immediately. Every sentence earns its place.
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 5-parameter tool with no annotations, the description is thin. It omits matching semantics (e.g., AND/OR combination), the role of the index parameter, and behavior when no element matches. The output schema likely covers return values, but selector construction guidance remains underspecified.
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. It adds a useful constraint ('Provide at least one selector field') but does not explain the meaning or interaction of individual parameters like text, text_contains, or resource_id. The property names are somewhat self-explanatory, but the description alone is insufficient for precise selector construction.
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 a specific verb ('Check') and resource ('element ... on screen'). The phrase 'currently exists' distinguishes it from wait_for_element and get_screen_elements by implying an immediate, non-waiting existence check. It is specific and 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 implies use for verifying immediate presence of an element, but it does not explicitly contrast this with sibling tools like wait_for_element or get_screen_elements. It gives no explicit when-to-use or when-to-use-alternative guidance.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.