gecko-mcp

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press_key

Press a keyboard key (e.g., Enter, Tab, Escape) on the active browser tab, or target a specific tab with browserId.

Instructions

Press a keyboard key in the page (e.g. "Enter", "Tab", "Escape", "ArrowDown"). Targets the active tab unless a browserId is given.

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": "press_key"
  }
}

Input Schema

Name	Required	Description	Default
`key`	Yes	Key name, e.g. "Enter".
`browserId`	No	Target tab (from list_tabs). Defaults to active.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv2.2.4Jun 20, 2026

TDQS

A4.1/5.0

Behavior3/5

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

Annotations declare readOnlyHint=false and destructiveHint=false, and the description's 'Press' action aligns with a non-read mutation. The description adds the active tab behavior, but does not disclose other behavioral traits like sequence effects or event propagation. Given annotations already convey non-read-only and non-destructive, the description provides modest additional value.

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?

Two sentences with no redundancy. The first sentence states the core action with examples; the second explains tab targeting. Every word is necessary and well-placed.

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

Completeness5/5

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

For a simple tool with two parameters and no output schema, the description fully covers the action, key parameter examples, and browserId behavior. An agent can correctly invoke it for pressing a key on the active or specified tab.

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

Parameters4/5

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

Schema coverage is 100%, and the description adds examples for the 'key' parameter and clarifies the optional 'browserId' parameter's effect ('Targets the active tab unless a browserId is given'). This goes beyond the brief schema descriptions, adding practical guidance.

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

Purpose5/5

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

The description clearly states the verb 'Press' and resource 'keyboard key', provides concrete examples ('Enter', 'Tab', 'Escape', 'ArrowDown'), and specifies scope ('in the page'). It implicitly distinguishes from siblings like 'real_key' (physical key press) and 'type_text' (typing text).

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

Usage Guidelines3/5

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

The description indicates that it targets the active tab unless a browserId is given, giving context for when to use the browserId parameter. However, it lacks explicit guidance on when to use this tool over alternatives (e.g., 'real_key' for physical key input), leaving the agent to infer based on naming.

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