firmauy-mcp-inspect 0.1.3

Read-only MCP server that brings FirmaUY signature inspection to your AI assistant. Offline, no smart card, no signing, redacted by default.

firmauy-mcp-inspect

firmauy-mcp-inspect is a small, read-only MCP server that lets an AI assistant inspect documents signed with a Uruguayan cédula de identidad using FirmaUY. It verifies signatures (PDF/PAdES, XAdES XML, or a detached CMS .p7s) and validates cédula check digits. Verification runs offline and does not require a smart card.

It exists for the one task where an assistant genuinely beats the bare CLI, triaging a batch of signed documents in plain language. Point it at a folder and it verifies every file, groups the results by issuing CA, and flags anything that is not VALID or whose certificate chain is not trusted, leaving you a summary to act on.

By design it only ever inspects. It cannot sign, never sees a PIN, and redacts the signer's personal data by default, so identities stay out of the model's context.

Scope (inspection only, by design)

FirmaUY can also sign with the national ID card and read the cardholder's data. This server deliberately exposes neither of them.

• No signing. A signature with a national ID is a legally significant act that needs the physical card and a PIN. A model must never be able to trigger it. Signing stays a human, manual action.
• No identity or photo. fetch-identity and fetch-photo return personal and biometric data. That must not flow into a model's context, so those commands are not exposed.

What the model sees from verification is redacted by default. The model receives the indication, the trust status, and the issuer (a public CA), but not the signer's name or document number.

Tools

Tool	What it does
verify(path, original=None, redact=True)	Verify one signed file (PDF/PAdES, XAdES XML, detached CMS/.p7s). Returns the indication, per-signature trust and checks.
verify_batch(paths, redact=True)	Verify many files. Returns a summary count by indication plus a compact per-file result (indication, trusted, issuing CA).
validate_ci(number)	Validate a cédula's check digit (arithmetic consistency only, not an identity check).
doctor()	Report the local setup status (PC/SC, PKCS#11 module, card, bundled CAs).

verify_batch handles self-contained signatures (PDF/PAdES, XAdES XML). A detached .p7s needs its original file, so verify those one at a time with verify(path, original=...).

Verification is offline, with certificate-chain validation up to the Uruguayan national root. A VALID result is a technical assessment, not a statement of legal validity. For authoritative verification, use AGESIC's official validator. This is an independent, unofficial tool, not affiliated with or endorsed by AGESIC.

Requirements

The firmauy CLI must be installed and on PATH.

uv tool install firmauy
firmauy --version

(Override the executable with the FIRMAUY_BIN environment variable if it lives elsewhere.)

Configuration

All are optional and configured through environment variables.

Variable	Default	Purpose
FIRMAUY_BIN	(found on PATH)	Path to the firmauy executable, if it is not on PATH.
FIRMAUY_MCP_TIMEOUT	60	Per-call timeout, in seconds, for each firmauy invocation.
FIRMAUY_MCP_MAX_WORKERS	8	Max concurrent verifications in verify_batch. Set to 1 for sequential.
FIRMAUY_MCP_ALLOWED_ROOTS	none (no limit)	Directories the tools may read from, separated by the OS path separator (: on Linux/macOS, ; on Windows). When set, any path outside them (after resolving symlinks and ..) is refused.
FIRMAUY_MCP_ALLOWED_EXTENSIONS	none (no limit)	Comma-separated types allowed for the signed file, e.g. .pdf,.xml,.p7s. Does not restrict a detached .p7s's original.

A malformed numeric override is ignored (it falls back to the default) rather than failing startup.

Sandboxing (recommended)

This server hands file paths from the model to firmauy, which opens them. Confining what it can read matters for a tool that touches national-ID signatures, so set both allowlists. They are opt-in and fail closed.

export FIRMAUY_MCP_ALLOWED_ROOTS="/srv/inbox/signed"
export FIRMAUY_MCP_ALLOWED_EXTENSIONS=".pdf,.xml,.p7s"

Containment is checked on the resolved, canonical path (symlinks and .. followed), so it is not fooled by traversal, symlink escapes, or sibling directories sharing a name prefix. The root allowlist also covers the original of a detached .p7s. The extension allowlist does not, because that original is arbitrary content.

Install

uv tool install firmauy-mcp-inspect

This puts the firmauy-mcp-inspect command on your PATH, which starts the server over stdio. You can also run it without installing, straight from PyPI, with uvx firmauy-mcp-inspect.

Try it interactively with the MCP Inspector.

npx @modelcontextprotocol/inspector firmauy-mcp-inspect

To work on it from a clone instead, run uv sync and then uv run firmauy-mcp-inspect.

Configure your client

Both forms below assume firmauy-mcp-inspect is on your PATH from uv tool install. If a GUI client cannot find it, use uvx as the command ("command": "uvx", "args": ["firmauy-mcp-inspect"]) or give the absolute path.

Claude Code

claude mcp add firmauy-inspect -- firmauy-mcp-inspect

Claude Desktop (claude_desktop_config.json)

{
  "mcpServers": {
    "firmauy-inspect": {
      "command": "firmauy-mcp-inspect"
    }
  }
}

Then ask it things such as "Verify every signed PDF in this folder, group them by issuing CA, and flag anything that is not VALID or whose chain is not trusted."

Tests

uv run pytest

The tests mock the firmauy subprocess, so they need neither the CLI nor a card. The path-sandboxing tests additionally create temporary files and a symlink on the local filesystem.

License

Apache-2.0.