Clear an input field and set its value in a session, replacing existing text via CSS selector; use when you need to overwrite form field values.
Clear an input field and set its value, replacing what was there (browser_type appends instead).
| Name | Required | Description | Default |
|---|---|---|---|
| value | Yes | Value to fill in | |
| selector | Yes | CSS selector of the input element | |
| session_id | Yes | Session ID returned by browser_navigate |
Changes observed during successful MCP inspections.
v2.7.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=false, destructiveHint=false and openWorldHint=true, so the write/exploration profile is covered. The description's useful addition is that it clears existing content before setting the value — a nuance not conveyed by destructiveHint=false — but it says nothing about required page state, element type constraints, or what happens on a non-input selector.
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 sentence, front-loaded with the operation and immediately followed by the sibling disambiguation. Nothing is redundant and every clause 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 three-parameter, fully schema-documented write tool with annotations covering safety and open-world behavior, the essential routing and semantics are present. Minor gaps remain around error/edge-case behavior (e.g. what happens if the selector matches a non-input element), which keeps it short of a 5.
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% and all three parameters are documented in the schema, so the schema carries the burden. The description adds no syntax, format, or selector-interpretation detail beyond what the schema provides — the baseline 3 for full-coverage schemas.
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 pairs a specific verb ('Clear ... and set its value') with the resource (an input field) and explicitly contrasts it with the sibling browser_type ('appends instead'). An agent can distinguish this from browser_type without opening either schema.
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 names the alternative tool by name and states the selecting condition: use browser_fill when you want to replace existing content, browser_type when you want to append. This is exactly the when/when-not/alternative guidance the tool needs given the near-identical sibling.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.