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@powforge/captcha-mcp

@powforge/captcha-mcp

by zekebuilds-lab
OverviewSchemaSourceRelated ServersDiscussionsAdmin
JavaScript
Remote

challenge

Obtain a fresh proof-of-work challenge for per-call authentication. Returns salt and difficulty; agent must find a nonce satisfying the PoW condition, then call verify.

Instructions

Request a fresh PoW challenge from the PowForge captcha service. Returns {id, salt, difficulty, signature, instructions}. The agent must find a nonce such that SHA-256(salt + nonce) has at least difficulty leading zero bits, then call the verify tool. Free tier — no payment required.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "challenge"
  }
}

Input Schema

NameRequiredDescriptionDefault

No arguments

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.2.0

TDQS

A4.5/5.0
Behavior4/5

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

With no annotations, the description carries full burden. It discloses the tool creates a new challenge (non-idempotent), returns specific fields, requires a subsequent PoW solution, and mentions free tier. Lacks rate limit info but is adequate.

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 concisely cover purpose, return structure, workflow, and free tier. No redundancies or fluff.

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?

The tool has no input schema and no output schema, so the description fully covers both: explains that no input is needed and details the returned object fields along with subsequent steps. Sufficient for a simple tool.

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?

No input parameters exist, so schema coverage is 100%. The description adds value by explaining the return structure, which is not parameter semantics but compensates for missing output 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 clearly states the verb 'Request' and resource 'fresh PoW challenge from PowForge captcha service', and distinguishes from sibling 'verify' by mentioning the complete workflow including the call to verify.

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 description explains when to use (requesting a captcha challenge) and what to do next (find nonce, call verify), but does not explicitly contrast with 'status' or provide when-not-to-use conditions.

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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