browser-mcp

browser_press

Simulate keyboard key presses in the browser. Use modifiers to combine with Alt, Ctrl, Meta, or Shift for automated testing and interactions.

Instructions

Press a key. modifiers is a bitfield: 1=Alt, 2=Ctrl, 4=Meta, 8=Shift.

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": {
      "key": "<key>"
    },
    "name": "browser_press"
  }
}

Input Schema

Name	Required	Description	Default
`key`	Yes
`modifiers`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Sep 18, 2026

TDQS

C2.9/5.0

Behavior2/5

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

With no annotations, the description must disclose behavioral implications, but it only says 'Press a key' and defines modifiers. It does not state that the key press targets the focused element, may trigger navigation or shortcuts, or whether it waits for resulting page changes.

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

Conciseness5/5

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

The description is extremely concise, leads with the core action, and every word is informative. No filler or redundancy.

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?

For a tool with no annotations and no output schema, this description is too thin. It lacks usage context, key-value guidance, and behavioral expectations, leaving an agent to guess at critical details for correct invocation.

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

Parameters3/5

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

Schema description coverage is 0%, so the description must compensate. It fully explains the modifiers bitfield values (1=Alt, 2=Ctrl, 4=Meta, 8=Shift), which is valuable, but it does not specify accepted key strings or syntax for the required key parameter.

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 phrase 'Press a key' clearly identifies the action as a keyboard key press, which distinguishes it from siblings like click, type, and fill at a basic level. However, it does not explicitly state that it acts on the current page or name alternatives, so it falls short of a 5.

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

Usage Guidelines2/5

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

No when-to-use or when-not-to-use guidance is provided; the description never mentions alternatives like browser_type or browser_click. An agent must infer when browser_press is appropriate instead of being told.

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