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umbra

umbra

by lxchx
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Remote

Rotate Fingerprint

rotate_fingerprint

Re-seeds canvas, audio, and WebGL noise mid-session to change a tab’s browser fingerprint when stealth mode is fully enabled at spawn.

Instructions

Re-seed canvas/audio/WebGL noise mid-session. Needs stealth_mode='full' at spawn.

Ex: rotate_fingerprint('t0') → {"new_seed":2937184832}

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": {
      "tab_id": "<tab_id>"
    },
    "name": "rotate_fingerprint"
  }
}

Input Schema

NameRequiredDescriptionDefault
tab_idYes

Output Schema

NameRequiredDescriptionDefault

No arguments

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

A3.9/5.0
Behavior3/5

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

With no annotations, the description carries the behavioral disclosure burden. It usefully states the stealth_mode prerequisite and the example output shape, but it does not explain failure behavior, whether changes are scoped to one tab, or what happens to existing session state beyond the seed.

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 two short sentences plus a compact example, with the core effect and prerequisite front-loaded. There is no wasted text.

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?

An output schema exists, so the response shape is covered, and the description adds the key spawn-time prerequisite and mid-session effect. The remaining gap is parameter semantics for tab_id, which prevents a perfect score.

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 0%, and the sole required parameter, tab_id, is undocumented. The example rotate_fingerprint('t0') hints that tab_id is a string tab identifier, but it does not explain where tab IDs come from or whether 't0' has special meaning.

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 states a specific verb, 'Re-seed', and specific resources, 'canvas/audio/WebGL noise', so the tool's effect is immediately clear. It also distinguishes the operation as 'mid-session', separating it from spawn-time fingerprint setup.

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 prerequisite 'Needs stealth_mode="full" at spawn' gives clear context for when this tool can be used. It does not explicitly compare against alternatives, but the mid-session re-seeding use case is clearly implied.

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

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