# captcha-mcp

> Use this tool when you need to verify user authenticity and prevent automated attacks in authentication flows. The captcha-mcp tool generates proof-of-work challenges and verifies solutions, providing a stateless and API-key-free verification process for trusted clients. It's ideal for embedding in authentication flows to prevent bots and ensure secure user verification.

Canonical page: https://skillsregistry.net/skills/zekebuilds-captcha-mcp  
JSON: https://api.skillsregistry.net/v1/skills/zekebuilds-captcha-mcp

## Description

PoW CAPTCHA verification for MCP clients. Exposes generate_challenge and verify_solution tools — stateless proof-of-work that agents can embed in auth flows. L402 Lightning skip tier available for trusted clients. No API key required for PoW path.

## Trust

- **Trust score (0–1):** 0.30
- **Verification tier:** unverified
- **Last scanned:** 2026-09-03

## Facts

- **Version:** 1.0.0
- **Skill type:** atomic
- **Execution layer:** mcp-remote
- **Runtime environment:** api
- **Category:** api-integration
- **Updated:** 2026-09-03

## Source

- **Source listing:** [Smithery](https://smithery.ai/server/zekebuilds/captcha-mcp)

## Use it

Resolve this record through the SkillsRegistry MCP server (no auth, read-only):

```
claude mcp add --transport http --scope user skillsregistry https://api.skillsregistry.net/mcp
```

```json
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "get_skill",
    "arguments": {
      "slug": "zekebuilds-captcha-mcp"
    }
  }
}
```

REST: `GET https://api.skillsregistry.net/v1/skills/zekebuilds-captcha-mcp` · pull for local use: `GET https://api.skillsregistry.net/v1/skills/zekebuilds-captcha-mcp/pull`

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SkillsRegistry indexes agent skills from public registries and GitHub. Skills we have analysed are scanned with Circle-IR and scored on six dimensions; each listing states its scan coverage. More: https://skillsregistry.net/llms.txt