Check a checkbox or radio control by targeting a snapshot ref or CSS selector, solving form selection in automated browser sessions.
Check a checkbox or radio control.
| Name | Required | Description | Default |
|---|---|---|---|
| pageId | No | Stable page ID; defaults to the session active page | |
| target | Yes | Snapshot ref such as e12, aria-ref=e12, or a unique CSS selector | |
| sessionId | No | Optional session ID; defaults to this MCP client active session |
Changes observed during successful MCP inspections.
v2026.8.14Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden of disclosing behavior. It states that the tool 'checks' a control, but it does not mention whether the action waits for element stability, what happens if the control is already checked, or whether it triggers events. This is minimal behavioral disclosure for a UI automation action.
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 a single, front-loaded sentence with no wasted words. It is concise and readable, although it is terse enough that it may under-specify behavioral details.
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?
Given the simple action and full schema coverage, the description is minimally adequate but leaves out behavioral nuances that could matter for correct use, such as whether it only works on visible/enabled controls or how it reports errors. With no output schema and no annotations, a bit more context would improve completeness.
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 100%, so the parameters are already well documented. The description adds no parameter-specific meaning beyond the schema; it does not clarify the 'target' format or default behavior of 'pageId' and 'sessionId', but the schema already covers those. Baseline 3 is appropriate.
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 uses a specific verb ('Check') and resource ('checkbox or radio control'), making the tool's purpose immediately clear. It does not explicitly distinguish from sibling tools like nex_browser_click or nex_browser_uncheck, but the resource constraint provides some differentiation.
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?
No guidance is provided on when to use this tool versus alternatives such as nex_browser_click or nex_browser_uncheck. The description implies it is for checking checkbox/radio controls, but it does not state exclusions, prerequisites, or how to decide among similar interaction tools.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.