Kustodyan

A Model Context Protocol server for the Kustodyan data-protection API (powered by the RegData Protection Suite). It lets AI agents and applications protect, unprotect and search sensitive data through Kustodyan's contextual transform engine — so data is tokenized, encrypted, anonymized or masked according to who is asking (a role) and what operation is requested, with every call auditable.

It speaks two transports from one binary:

• stdio (default) — for local use (node dist/server.js after a build)
• streamable HTTP — for hosting behind a reverse proxy (set KUSTODYAN_MCP_TRANSPORT=http)

What it does

The Kustodyan Engine exposes a single transform operation; behaviour is selected by evidence you send — a Role (who) and an Action (Protect / Unprotect / Search) — plus the (className, propertyName) of each value. The transformation technique (encryption, tokenization, anonymization, masking) is configured server-side, never chosen by the caller. This server wraps that model in ergonomic tools.

Tools

Tool	Purpose
protect	Protect field values for a role (encrypt / tokenize / anonymize per config).
unprotect	Reverse a protection to recover the original — returns cleartext, treat as sensitive.
search	Get a search token to match against a stored protected value.
transform	Low-level escape hatch: send a full Engine transform payload.
validate_transform	Statically validate a transform payload before sending.
whoami	Confirm credentials and the configured environment (decoded token claims).
health	Check Identity + Engine reachability.
list_data_model	Discover the configured classes, properties, roles and actions.

Resources & prompts

• kustodyan://guide/contextualisation — how Role/Action evidence drives transforms.
• kustodyan://guide/best-practices — safe, effective use of protect/unprotect.
• kustodyan://data-model — the configured data-model manifest.
• Prompt protect_record — guides an assistant to protect a record's PII safely.

Configuration (environment)

Variable	Required	Description
KUSTODYAN_IDENTITY_URL	yes	e.g. https://<env>.kustodyan.io/api/identity
KUSTODYAN_ENGINE_URL	yes	e.g. https://<env>.kustodyan.io/api/engine
KUSTODYAN_CLIENT_ID	yes	Engine API client id (from the CoreAdmin portal)
KUSTODYAN_CLIENT_SECRET	yes	Engine API client secret
KUSTODYAN_DATA_MODEL	no	Path to a data-model manifest JSON (classes/properties/roles)
KUSTODYAN_MCP_TRANSPORT	no	stdio (default) or http
KUSTODYAN_HTTP_HOST / KUSTODYAN_HTTP_PORT	no	HTTP bind (default 127.0.0.1 / 9090)

Run locally (stdio)

npm install && npm run build
KUSTODYAN_IDENTITY_URL=https://<env>.kustodyan.io/api/identity \
KUSTODYAN_ENGINE_URL=https://<env>.kustodyan.io/api/engine \
KUSTODYAN_CLIENT_ID=... KUSTODYAN_CLIENT_SECRET=... \
node dist/server.js

MCP client config (stdio):

{
  "mcpServers": {
    "kustodyan": {
      "command": "node",
      "args": ["/path/to/kustodyan-mcp/dist/server.js"],
      "env": {
        "KUSTODYAN_IDENTITY_URL": "https://<env>.kustodyan.io/api/identity",
        "KUSTODYAN_ENGINE_URL": "https://<env>.kustodyan.io/api/engine",
        "KUSTODYAN_CLIENT_ID": "...",
        "KUSTODYAN_CLIENT_SECRET": "..."
      }
    }
  }
}

Run hosted (HTTP, token-gated image)

The container serves streamable HTTP behind an nginx bearer-token gate.

docker run -d -p 8080:8080 \
  -e MCP_BEARER_TOKEN=<a long random secret> \
  -e KUSTODYAN_IDENTITY_URL=https://<env>.kustodyan.io/api/identity \
  -e KUSTODYAN_ENGINE_URL=https://<env>.kustodyan.io/api/engine \
  -e KUSTODYAN_CLIENT_ID=... -e KUSTODYAN_CLIENT_SECRET=... \
  <image>

Point your MCP client at https://<host>/mcp, sending Authorization: Bearer <MCP_BEARER_TOKEN> (or ?token=<MCP_BEARER_TOKEN>). GET /healthz is unauthenticated for probes.

Build

npm install
npm run build      # -> dist/
npm start          # stdio

Safety notes

• unprotect returns cleartext. Never log it, persist it, or call it for an unauthorised role. Prefer a masking role when a partial value suffices.
• Discover the data model (list_data_model) instead of guessing propertyNames.
• Transform calls can succeed (HTTP 200) while individual fields carry a per-field error — always inspect per-field results.

Documentation

• docs/rps-api-contract.md — the verified Identity + Engine API contract (auth, /transform shape, error model) this server is built on.
• docs/searchable-encryption.md — the searchable-encryption guide: the scheme/leakage ladder, and the PROPE search-band contract (dependencyContext {method,min,max}, case-insensitive collation).

License

MIT