bc-rig

browser_act

Act on browser elements using @b refs from browser_observe. Supports click, fill, navigate, and key press; returns updated state.

Instructions

Act in the selected project browser. Use an @b ref from browser_observe; returns changed state.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "action": "<action>"
    },
    "name": "browser_act"
  }
}

Input Schema

Name	Required	Description	Default
`key`	No	Playwright key such as Enter or Escape
`url`	No
`value`	No	Text for fill; never echoed or stored
`action`	Yes
`target`	No	@b ref preferred; otherwise exact accessible name
`observe`	No		changes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv3.0.0Jul 27, 2026

TDQS

B3.2/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations indicate readOnlyHint=false and destructiveHint=false, so the tool modifies state but is not destructive. The description adds 'returns changed state,' which aligns with mutation. No further behavioral details are provided, but the annotations cover the safety profile adequately.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness3/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is very short (one sentence), which is concise, but it lacks important details for an agent to fully understand usage. It is front-loaded with 'Act,' but the brevity reduces utility.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool has 6 parameters, 1 required, no output schema, and no nested objects, the description is insufficient. It does not explain the action enum, the observe options, or the url parameter. The tool's complexity demands more context.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters2/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 50% for 6 parameters, but the description adds zero parameter-level details. The schema itself describes some parameters (e.g., key, value, target, observe), but the description does not compensate for the missing 50% coverage or provide additional meaning.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description states the tool acts in the selected project browser and returns changed state, distinguishing it from browser_observe and browser_screenshot. However, 'act' alone is vague; the action enum is only in the schema. It clearly specifies the use of @b refs, which adds clarity.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explicitly says to use an @b ref from browser_observe, providing a clear step to obtain the ref before acting. This guides the agent on workflow but does not explicitly state when to avoid the tool or list alternatives.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

Deploy Server