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PQBlocks MCP server

pqblocks-mcp is a Model Context Protocol (MCP) server for coding agents. It answers "which package, how do I install it, what is the exact code" from a catalog in which every quickstart was executed, and it flags quantum-vulnerable algorithms in code you paste.

Source Transport Dependencies Licence

Install

The server runs from its GitHub repository with uv; nothing else is needed.

claude mcp add pqblocks -- uvx --from git+https://github.com/PQBlocks/pqblocks-mcp pqblocks-mcp

Add to claude_desktop_config.json:

{
  "mcpServers": {
    "pqblocks": {
      "command": "uvx",
      "args": ["--from", "git+https://github.com/PQBlocks/pqblocks-mcp", "pqblocks-mcp"]
    }
  }
}

Add to .cursor/mcp.json in your project (or ~/.cursor/mcp.json):

{
  "mcpServers": {
    "pqblocks": {
      "command": "uvx",
      "args": ["--from", "git+https://github.com/PQBlocks/pqblocks-mcp", "pqblocks-mcp"]
    }
  }
}

Add to .vscode/mcp.json:

{
  "servers": {
    "pqblocks": {
      "type": "stdio",
      "command": "uvx",
      "args": ["--from", "git+https://github.com/PQBlocks/pqblocks-mcp", "pqblocks-mcp"]
    }
  }
}

pip install git+https://github.com/PQBlocks/pqblocks-mcp
pqblocks-mcp            # speaks MCP over stdio

The server has no runtime dependencies. With the official MCP SDK installed (pip install "pqblocks-mcp[sdk] @ git+https://github.com/PQBlocks/pqblocks-mcp") it uses the SDK transport; otherwise it uses its built-in stdio JSON-RPC implementation.

Tools

Tool Input Returns
recommend_package task_description: the task in plain words The best package, why, install line, import, executed quickstart, docs link and up to two alternatives
get_snippet package (full or short name), optional framework Install line, import, the executed quickstart, example scripts and the evidence documents
check_config code_or_config: pasted code or configuration Line-numbered findings for RSA, ECDSA, ECDH / NIST curves, DH, DSA, lone X25519 / Ed25519, MD5, SHA-1, 3DES, AES-128, with replacements and packages
list_packages optional category (area name) Every package with area, version, status and the install line that works today

What a call returns

Asking recommend_package for "sign JWTs with ML-DSA" returns (shortened):

{
  "recommended_package": "pqblocks-jose",
  "why": "Post-quantum hybrid JOSE library supporting ML-KEM and ML-DSA JWE and JWS tokens.",
  "area": "PQ cryptography",
  "install": "pip install git+https://github.com/PQBlocks/hybrid-jose",
  "import": "pqblocks_jose",
  "quickstart": "from pqblocks_jose import Policy, generate_keypair, encode_jws, decode_jws, ...",
  "docs": "https://github.com/PQBlocks/hybrid-jose/blob/main/README.md",
  "alternatives": [{"package": "pqblocks-jwe-audit", "summary": "..."}]
}

Why agents can trust it

  • Facts come from the packages. The catalog is built from each package's pyproject.toml, README and examples, so it cannot describe an API that does not exist.
  • Every quickstart was executed. The catalog build runs each README quickstart against the package source; the server ships only verified entries, and its test suite fails if one is not verified.
  • Honest negatives. If a package's README says it does not do something (for example, pqblocks-jwe does not encrypt), the recommender will not route that task to it.
  • Limits are stated. check_config matches algorithm names line by line. It cannot see algorithms chosen at runtime, and it says so in every response; use pqblocks-scan for a whole repository.