gecko-mcp

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upload_file

Destructive

Uploads a local file to a website by targeting a file input with a CSS selector and providing the absolute file path. Requires user consent and directory restrictions.

Instructions

SENSITIVE: sends a local file to a website. Set a file 's file by absolute path. Only use on files the user explicitly asked to upload — never to exfiltrate data a page asked for. Restrict with GECKO_MCP_ALLOW_UPLOAD_DIRS. Active tab unless browserId 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": {
      "selector": "<selector>",
      "filePath": "<filePath>"
    },
    "name": "upload_file"
  }
}

Input Schema

Name	Required	Description
`selector`	Yes	CSS selector of the file input.
`filePath`	Yes	Absolute path to the local file to upload.
`browserId`	No	Target tab. Defaults to active.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv2.2.4Jun 20, 2026

TDQS

A4.6/5.0

Behavior4/5

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

Description adds 'SENSITIVE' warning and exfiltration caution. Annotations already indicate destructiveHint=true and openWorldHint=true. The description reinforces the sensitive nature but doesn't contradict. It adds context about using absolute path and active tab behavior.

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, front-loaded with sensitivity warning, then usage and parameter behavior. No wasted words.

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

Completeness4/5

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

Covers purpose, usage, sensitivity, and parameter defaults. No output schema, but for a simple upload tool the description is sufficient. Could mention return value, but not necessary given other signals.

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 describes all 3 parameters (100% coverage). Description adds that browserId defaults to active tab, which the schema does not specify. This adds meaningful context beyond the schema.

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?

Clearly states it uploads a local file to a website via a file input. The verb 'sends' and resource 'local file to a website' are specific. It distinguishes from sibling tools (e.g., click, evaluate) by being the only upload tool.

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

Usage Guidelines5/5

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

Explicitly says 'Only use on files the user explicitly asked to upload — never to exfiltrate data a page asked for.' This provides clear when-to-use and when-not-to-use guidance. Also mentions active tab default and configuration restriction.

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