Set an input field's value and trigger input/change events for reliable form updates and browser automation.
Set an input's value (fires input/change).
| Name | Required | Description | Default |
|---|---|---|---|
| ref | No | ref from snapshot, e.g. e3 | |
| tab | No | tab id, defaults to current | |
| force | No | ||
| value | Yes | string, or array of strings for multi-select | |
| timeout | No | ||
| selector | No | CSS selector | |
| request_timeout | No | Outer page request deadline in milliseconds; defaults to at least 30000 |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full disclosure burden. It does earn credit for stating that input/change events fire, which is real behavioral information beyond the schema, but it omits whether existing content is replaced or appended, what force bypasses, and what happens on failure or timeout.
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?
A single short sentence with the core action front-loaded and the event side effect in parentheses – no wasted words. Brevity here comes at the cost of under-specification, but the sentence itself is well-formed.
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 7-parameter mutation tool with no annotations and no output schema, one line is not enough. Missing are ref vs selector precedence, replacement semantics, force behavior, and any notion of what the tool returns or how it errors.
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 71% with 7 parameters, and the description adds nothing about the three undocumented ones: 'force', 'timeout', and 'value' formats beyond the vague 'set an input's value'. The riskiest parameter, 'force', is left completely unexplained in both description and 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?
States a specific verb and resource: 'Set an input's value', plus the notable side effect of firing input/change events. It does not differentiate itself from the close siblings 'type' and 'fill_form', which is the main gap at this level.
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?
There is no guidance on when to use this instead of 'type' (keystroke-by-keystroke) or 'fill_form' (bulk), nor any prerequisites such as needing a ref from 'snapshot' or a selector. The agent must infer the choice entirely from sibling names.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.