captchasonic-setup

captchasonic-setup is a skill for Claude Code, Codex from Captcha-Sonic/Agent-skills. It costs 51 tokens per session (781 once invoked), scanned A, original, MIT.

A setup guide for connecting CaptchaSonic, an online service that solves CAPTCHA challenges, to an AI agent through an MCP server. It covers installation, API-key configuration, and connection checks.

In plain words
What is it for?
It is for checking prerequisites, adding the CaptchaSonic server to Claude Code or Claude Desktop, and verifying that the connection works.
Why use it?
It removes the guesswork from installing the server and setting the required environment variable.

Skill for Claude CodeCodex

Part of the captchasonic plugin — 4 skills, 1 MCP server shipped together

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/captcha-sonic/agent-skills/captchasonic-setup
Any agent
npx skills add Captcha-Sonic/Agent-skills --skill captchasonic-setup
Clone the repo
git clone --depth 1 https://github.com/Captcha-Sonic/Agent-skills

Made for: Claude Code, Codex.

Or install captchasonic, the plugin that ships this one along with the rest of its 4 skills, 1 MCP server.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for captchasonic-setup

README.md
[![agentmods](https://agentmods.dev/badge/skills/captcha-sonic/agent-skills/captchasonic-setup.svg)](https://agentmods.dev/skills/captcha-sonic/agent-skills/captchasonic-setup)
Your own site
<a href="https://agentmods.dev/skills/captcha-sonic/agent-skills/captchasonic-setup"><img src="https://agentmods.dev/badge/skills/captcha-sonic/agent-skills/captchasonic-setup.svg" alt="Measured on agentmods" height="20"></a>
Per session 51 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 781 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00051 $0.00781
Opus 5 $0.00026 $0.00391
Sonnet 5 $0.00010 $0.00156
Haiku 4.5 $0.00005 $0.00078

Measured 4d ago against content hash 133d1baf6557, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

captchasonic-setup scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 4d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/captchasonic-setup/SKILL.md · 126 lines

How it starts

The opening of the file, as written. The whole thing — 126 lines — stays where its author put it; the contents beside it link to each section on GitHub.

CaptchaSonic MCP Server Setup

Set up the CaptchaSonic MCP server so your AI agent can solve CAPTCHAs.

Step 1: Check Prerequisites

Verify Node.js is installed (v18+):

node --version

If not installed, the user needs to install Node.js from nodejs.org.

Step 2: Get the API Key

Ask the user for their CaptchaSonic API key. It starts with sonic_.

If they don't have one: "Register for free at captchasonic.com to get your API key."

Step 3: Add the MCP Server

Option A: Claude Code CLI (recommended)

claude mcp add sonic --env SONIC_API_KEY=sonic_xxxx -- npx -y @captchasonic/mcp-server

Replace sonic_xxxx with the user's actual API key.

Option B: Global Install + CLI

npm install -g @captchasonic/mcp-server
claude mcp add sonic --env SONIC_API_KEY=sonic_xxxx -- sonic-mcp

Option C: Claude Desktop

Edit the Claude Desktop config file.

macOS: ~/Library/Application Support/Claude/claude_desktop_config.json Windows: %APPDATA%\Claude\claude_desktop_config.json

Add this to the mcpServers section:

{
  "mcpServers": {
    "sonic": {
      "command": "npx",
      "args": ["-y", "@captchasonic/mcp-server"],
      "env": {
        "SONIC_API_KEY": "sonic_xxxx"
      }
    }
  }
}

Then restart Claude Desktop.

Option D: Antigravity IDE

Add MCP server configuration in your Antigravity settings pointing to:

npx -y @captchasonic/mcp-server

with environment variable SONIC_API_KEY=sonic_xxxx.

Step 4: Verify Health Check

After adding the server, run a health check to confirm connectivity:

Tool: health_check
Arguments: {}

Expected response:

healthy: true
version: x.x.x

If the health check fails:

  • Check your internet connection
  • Verify Node.js is installed and npx is available
  • Try running npx -y @captchasonic/mcp-server manually to see errors

Step 5: Verify API Key

Run a balance check to confirm the API key is valid:

Read the full file on GitHub · 126 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 4d ago First seen · 126 lines · 51 tokens per session scan A 133d1baf6557

Subscribe to this mod's changes

captchasonic-setup is a skill published in the GitHub repository Captcha-Sonic/Agent-skills (1 stars, last pushed 3mo ago), licensed MIT. It adds 51 tokens to every session and 781 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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