The Model Context Protocol server at @iso-compliant/mcp-server is the IDE-and-agent distribution wedge. Free-tier tools (IBAN / QRR / SCOR checksums, structured-address lint, ISO 20022 field reference) run pure-local with no network and no API key. Paid tools (pain.001, camt.053, pain.002, Swiss QR-bill) proxy to https://api.iso-compliant.com under a bearer token.
Two transports: stdio for local Claude Desktop / Cursor / VS Code installs, HTTP+SSE for remote-hosted agents at https://mcp.iso-compliant.com/sse.
Locale-aware tool descriptions: en / de / fr / it (set via ISOCOMPLIANT_MCP_LOCALE env var).
12 tools total. The free tier exists so an agent that does not have a key can still answer "is this IBAN valid?" or "is this address structured-mandate ready?" — that path is the surface-area maximiser. See the packages/mcp-server/README.md for install snippets and the tool catalog.