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Using AI coding assistants for ISO 20022 — the MCP wedge

How an MCP server gets ISO 20022 expertise into Claude / Cursor / VS Code without your team having to remember the field paths.

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A typical ISO 20022 question — "what is the camt.053 carrier field that JPMorgan preserves end-to-end?" — is answerable in a quiet 20 minutes with the ISO 20022 catalog, the JPMorgan ACCESS implementation guide, and a coffee. The same question routed through Claude or Cursor today returns either a confident wrong answer (JPMorgan uses EndToEndId — common confident wrong) or a hedged "I don't have that information".

The MCP-server fix: ship a tool the agent calls directly. The agent does not have to remember anything about ISO 20022; it asks the tool, the tool returns a deterministic answer, the agent surfaces it.

What the MCP server ships

@iso-compliant/mcp-server ships 12 tools, split into a free pure-local tier (no API key, runs in the IDE) and a paid network tier (proxies to api.iso-compliant.com under a bearer token):

  • isocompliant.validate_iban — mod-97 + QR-IBAN flag. Pure local, no key.
  • isocompliant.compute_qrr — QRR mod-10 (Lührmann) check digit. Pure local.
  • isocompliant.compute_scor — SCOR mod-97 check digits. Pure local.
  • isocompliant.lint_address — structured-address mandate field-presence check. Pure local.
  • isocompliant.iso20022_field_reference — look up a field path (e.g. PstlAdr.StrtNm) and return the spec definition, max length, character set. Pure local.
  • isocompliant.build_pain001 — proxies to POST /v1/iso20022/pain.001. Paid.
  • isocompliant.parse_camt053 — proxies to POST /v1/iso20022/camt.053/parse. Paid.
  • isocompliant.classify_pain002 — proxies to POST /v1/iso20022/pain.002/parse. Paid.
  • isocompliant.render_qr_bill — proxies to POST /v1/qr-bill. Paid.
  • isocompliant.restructure_address — proxies to POST /v1/address/restructure. Paid.
  • isocompliant.reconcile — proxies to POST /v1/reconcile. Paid.
  • isocompliant.export_evidence — proxies to POST /v1/evidence/export. Paid.

The free-tier tools are the surface-area maximiser. An agent that does not have a paid key can still answer the "is this IBAN valid?" or "does this address have all five structured fields?" question. The free tier is the wedge — the agent uses it, the developer wins, the developer hits a question that needs the paid tier, the developer buys.

Setup

Claude Desktop / Cursor / VS Code with the MCP extension. One JSON snippet in the config file:

{
  "mcpServers": {
    "iso-compliant": {
      "command": "npx",
      "args": ["-y", "@iso-compliant/mcp-server"],
      "env": { "ISOCOMPLIANT_API_KEY": "iso_live_..." }
    }
  }
}

Restart the IDE. The agent sees the 12 tools alongside its built-in toolset and can invoke any of them at will.

Real-world prompts

Three patterns we see in production:

Pattern 1 — "Build me a pain.001 for this payroll batch"

Developer pastes a CSV of payee names + IBANs + amounts. Agent generates the JSON request, calls isocompliant.build_pain001, returns the XML + the audit sha256. Developer drops the XML into their bank-channel SFTP outbox.

Pattern 2 — "Why did this camt.053 entry not reconcile?"

Developer pastes a camt.053 XML snippet and an expected-invoice-id list. Agent calls isocompliant.parse_camt053, returns the candidate carriers, then walks the candidates against the expected list. Often the answer is "the EndToEndId was stripped by an intermediary; the durable carrier is AcctSvcrRef which contains the bank-side reference, not your invoice id — you need to match on Ustrd which carries INV-2026-001234".

Pattern 3 — "Is this address structured-mandate ready?"

Developer pastes a freeform address. Agent calls isocompliant.lint_address (pure local, no key needed) and returns the compliance verdict + the list of missing fields. If the developer wants the restructured form, the agent calls isocompliant.restructure_address (paid).

Why this is a moat

The MCP distribution path is the future of developer-tool adoption. A developer no longer integrates a library — they invoke a tool through the agent. The library that gets shipped via MCP wins the distribution. The free-tier tools (no key, no friction) are the surface-area land-grab; the paid-tier tools are the monetisation.

For a buyer evaluating ISO 20022 vendors today, "does it work in my IDE under Claude / Cursor?" is increasingly a procurement-grade question. iso-compliant's answer is yes, with twelve tools shipping today.

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