Fill one or more form controls in a specified order across a browser page, targeting each field by snapshot ref or unique CSS selector to automate data entry.
Fill one or more form controls in order.
| Name | Required | Description | Default |
|---|---|---|---|
| fields | Yes | ||
| pageId | No | Defaults to the active page | |
| sessionId | No | Defaults to the active session |
Changes observed during successful MCP inspections.
v2026.10.24Input schema / properties / fields / items / properties / target / descriptionPrevious value: -"Snapshot ref such as e12, aria-ref=e12, or a unique CSS selector"New value: +"Snapshot ref (e12) or unique CSS selector"Input schema / properties / pageId / descriptionPrevious value: -"Stable page ID; defaults to the session active page"New value: +"Defaults to the active page"Input schema / properties / sessionId / descriptionPrevious value: -"Optional session ID; defaults to this MCP client active session"New value: +"Defaults to the active session"v2026.8.14Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full disclosure burden, and it only hints that fields are applied sequentially. It says nothing about whether a snapshot/ref must exist first, what happens on a missing or ambiguous target (error vs. partial fill), or whether the fill dispatches input/change events.
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 well-formed sentence with no padding, and the ordering detail is front-loaded. It is concise to the point of under-specification for a tool with seven similar siblings.
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?
No annotations, no output schema, and a crowded sibling namespace mean the description should explain prerequisites, target resolution, and failure behavior. None of that is present, leaving an agent to guess at the most consequential details of a mutating browser action.
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 67% and the schema already documents 'target' as a snapshot ref or CSS selector plus pageId/sessionId defaults. The description's 'one or more ... in order' adds the batch and ordering semantics that the array schema does not state, which is real added value, but the value type and per-field validation remain unexplained.
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 verb and resource ('Fill ... form controls'), so the basic action is clear, but it offers no differentiation from close siblings like nex_browser_type, nex_browser_fill_account, nex_browser_fill_credentials, nex_browser_select_option, or nex_browser_check. An agent cannot tell from this text alone which one applies to a given field.
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 only guidance is the implicit 'one or more ... in order' batch/sequence detail. There is no statement of when to use this versus nex_browser_type or select_option, no prerequisite about needing a snapshot first, and no exclusions.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.