camt-exceptions: ISO 20022 Exceptions & Investigations, generated + XSD-valid

Generate and validate ISO 20022 Exceptions & Investigations (E&I) camt messages — with an MCP server. Starts with camt.056 (FI-to-FI Payment Cancellation Request): the message a bank sends to recall or cancel a payment it already dispatched — a duplicate, an erroneous amount, a fraud recall. Output is validated against the official bundled XSD before it's returned.

Latest release: v0.0.2 — camt.056 + camt.029 generation + validation, 4 MCP tools over stdio, 100% branch coverage, for Python 3.10+. Part of the ISO 20022 MCP suite. Additional E&I messages (camt.029, camt.026, camt.027, camt.087) plug into the same engine.

Why E&I

When a payment goes wrong, the fix is an Exceptions & Investigations message — and these are the least tooled corner of ISO 20022. camt.056 alone covers the single most common need: "I need to cancel/recall that payment." This library makes it a one-call, schema-valid operation for an agent, with the same depth as the credit-transfer generators elsewhere in the suite.

Install

pip install camt-exceptions
# or run the MCP server without installing:
uvx camt-exceptions

MCP client config (e.g. Claude Desktop):

{
  "mcpServers": {
    "camt-exceptions": {
      "command": "camt-exceptions-mcp"
    }
  }
}

Quick start — cancel a payment

from camt_exceptions import generator as g

xml = g.generate_message("camt.056.001.12", {
    "assignment_id": "CXL-001",
    "assigner_agent_bic": "DEUTDEFF",
    "assignee_agent_bic": "COBADEFF",
    "creation_date_time": "2026-03-02T10:00:00",
    "original_msg_id": "MSG-ORIG-001",
    "original_msg_nm_id": "pacs.008.001.08",
    "transactions": [{
        "original_end_to_end_id": "E2E-001",
        "original_interbank_settlement_amount": "1000.00",
        "original_interbank_settlement_currency": "EUR",
        "cancellation_reason_cd": "DUPL",       # duplicate payment
    }],
})
assert g.validate_xml("camt.056.001.12", xml)["is_valid"]   # True

Tools

Supported messages

Each new message plugs into the same engine: bundle its official XSD + template.xml and register it in MESSAGE_TYPES. Generated output is always XSD-validated before return, so correctness is machine-checked, not asserted.

Note: the payment-status and return messages of the E&I family — pacs.002 (Payment Status Report) and pacs.004 (Payment Return) — are already generated, XSD-valid, by pacs008-mcp.

The suite

Part of a family of vendor-neutral, Python-native ISO 20022 MCP servers:

• iso20022-mcp — unified gateway across the families.
• pain001-mcp · pacs008-mcp · camt053-mcp · acmt001-mcp — per-family servers.
• reconcile-mcp — statement/payment reconciliation.

Development

git clone https://github.com/sebastienrousseau/camt-exceptions
cd camt-exceptions
python -m venv .venv && . .venv/bin/activate
pip install -e . && pip install pytest pytest-cov ruff black mypy
pytest                      # 100% branch coverage gate; output is XSD-validated
ruff check camt_exceptions tests && black --check camt_exceptions tests && mypy camt_exceptions

Licence

Code licensed under the Apache License, Version 2.0. Bundled ISO 20022 message schemas (*.xsd) are © ISO 20022 and redistributed under the ISO 20022 terms; they are the same schemas published at iso20022.org.

mcp-name: io.github.sebastienrousseau/camt-exceptions