Achlens
Local-first MCP server and CLI for validating and generating synthetic ACH files.
Runs on your machine from its package; the steps are below.
What it does
- Reads
- Writes
- High impact
At most: creates or changes data: records, files, settings.
What it costs
FreeOdel charges nothing per call. The publisher may charge for its own service.
Runs locally over stdio
This server isn't hosted — your MCP client launches it from a package registry. Use one of the commands below, or drop the config into your client (e.g. Claude Desktop).
Run
uvx achlens
MCP client config
{
"mcpServers": {
"achlens": {
"command": "uvx",
"args": [
"achlens"
]
}
}
}achlens is a local-first Python MCP server and CLI for inspecting synthetic ACH files. It parses fixed-width records, validates structure and control totals, explains findings, masks sensitive fields, repairs derived controls, and generates deterministic test files. It never transmits ACH files or makes bank/network calls.
Use synthetic data only. This project is not a bank gateway, compliance advisor, or transmission system.
Quick Start
uv sync
uv run achlens --help
uv run achlens validate tests/fixtures/golden/sample_valid.ach
uv run achlens generate --sec PPD --entries 5 --seed 7 > synthetic.ach
In Windows PowerShell, use an explicit ASCII encoding because PowerShell's
default > redirection can write UTF-16 output that is not valid ACH text:
uvx achlens generate --sec PPD --entries 5 --seed 7 |
Set-Content -Encoding ascii synthetic.ach
Run the MCP server over stdio:
uv run achlens serve
The MCP server exposes validation, summaries, parsed-record paging, control explanations, routing checks, code lookup, synthetic generation, and control repair. See docs/tools.md for the current tool surface.
Sensitive fields are masked by default. Configure ACHLENS_ALLOWED_ROOTS to
enable MCP path inputs; otherwise provide file content directly. See
SECURITY.md for the data and write boundaries.
Development
This project uses uv.
uv sync
uv run achlens --help
uv run pytest -q
uv run ruff check .
uv run ruff format --check .
uv run mypy --strict src
Never add real payment data, account numbers, or ACH files to this repository.
