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nodriver-mcp-server

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Solve Cloudflare challenge

cf_verify

Solve Cloudflare 'Verify you are human' challenges by detecting and clicking the checkbox widget. Use this when a page is stuck on a browser-checking interstitial.

Instructions

Attempt to solve a Cloudflare "Verify you are human" challenge.

Use when a page is stuck on a Cloudflare interstitial — a checkbox widget, or "Checking your browser before accessing". Drives nodriver's built-in verification bypass, which locates the checkbox visually and clicks it.

Needs opencv, which is an optional extra: install nodriver-mcp[cf], or this reports that it is missing rather than failing obscurely. Many challenges clear by themselves after a few seconds, so wait_for(["some text from the real page"]) is worth trying first — and this says so when it looks at the page and finds no challenge at all.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
browserNoWhich browser to act on. Each name is an independent Chrome, created on first use. Omit for the shared default; parallel agents each need their own name.default

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv2.5.0
    • addedInput schema / properties / browser
      Added value: +{
+  "default": "default",
+  "description": "Which browser to act on. Each name is an independent Chrome, created on first use. Omit for the shared default; parallel agents each need their own name.",
+  "type": "string"
+}
  2. First observedv1.7.2

TDQS

A4.5/5.0
Behavior4/5

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

Annotations already indicate readOnlyHint=false and idempotentHint=false, implying side effects. The description adds valuable context: it drives nodriver's built-in bypass, locates and clicks the checkbox visually, requires the optional opencv dependency (and reports missing it gracefully), and handles the no-challenge case. It does not contradict annotations and enriches the behavioral picture beyond them.

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 five sentences with zero fluff. The purpose is front-loaded in the first sentence, usage conditions follow, then dependency and alternative guidance are given concisely. Every sentence earns its place; it is efficient and well-organized.

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 specialized challenge-solving tool, the description covers when to use, the alternative (wait_for), the optional dependency, and the no-challenge fallback. An output schema exists (indicated) to handle return values, so nothing critical is missing. The tool is fully comprehensible and actionable for an agent.

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?

The schema description coverage is 100% — the single optional 'browser' parameter is fully described in the schema, including its default and the semantics of naming independent Chrome instances. The tool description adds no further parameter-specific information, so it does not exceed the baseline set by 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?

The description opens with a specific verb and resource: 'Attempt to solve a Cloudflare Verify you are human challenge.' It precisely names the interstitial types (checkbox widget, 'Checking your browser') and is clearly distinct from all sibling tools, none of which target Cloudflare challenges. This leaves no ambiguity about what the tool does.

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?

It explicitly states when to use the tool ('Use when a page is stuck on a Cloudflare interstitial') and gives a concrete alternative: 'wait_for([some text from the real page]) is worth trying first' for challenges that self-resolve. It also explains that the tool reports when no challenge is present, covering the fallback condition. This is exemplary usage guidance.

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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