paperclip/packages/kv-demo-mcp-server

KV Demo MCP Server

A standalone, self-contained MCP server for demos. One process exposes four key/value MCP tools and a tiny web UI that renders the values those tools mutate — so you can call a tool from a Paperclip agent and watch the value appear in a browser tab.

The shared in-memory store is the whole point: the same Map<string, string> backs every tool call and every UI render. There is no database, no file, no persistence. Restart the process and the store is empty again. That makes this the right fixture for showing what Paperclip stores versus what the demo package stores — the package stores the values, Paperclip stores the connection, the profile/policy decisions, and the audit log.

This package pairs with the operator guide in doc/MCP-ACCESS-GOVERNANCE.md and the recorded walkthrough in doc/MCP-DEMO-SCRIPT.md.

What you get

• Four MCP tools (over the Streamable HTTP transport):
  • kv_list (read) — list every key/value, optionally filtered by prefix.
  • kv_get (read) — read one key.
  • kv_set (write) — set one key to a string value.
  • kv_delete (destructive) — delete a key. Carries destructiveHint: true so Paperclip's catalog quarantines it on first sight.
• A Values UI at / — an auto-refreshing HTML table over the same store.
• A JSON state route at /api/state — what the UI polls.

Local startup

From the repo root:

pnpm --filter @paperclipai/kv-demo-mcp-server build
pnpm --filter @paperclipai/kv-demo-mcp-server start

Or run the source directly during development:

cd packages/kv-demo-mcp-server
node --experimental-strip-types src/main.ts   # Node 24+

By default it listens on http://127.0.0.1:8848 and prints three URLs to stderr on startup:

• MCP endpoint — POST http://127.0.0.1:8848/mcp (Streamable HTTP)
• Values UI — GET http://127.0.0.1:8848/ (auto-refreshes every 2s)
• JSON state — GET http://127.0.0.1:8848/api/state

Open the Values UI in a browser tab and keep it visible. Every successful kv_set / kv_delete lands in that table within ~2 seconds.

Configuration

All configuration is via environment variables:

Variable	Default	Purpose
PORT (or KV_DEMO_PORT)	8848	Listen port. Use 0 for a random free port.
KV_DEMO_HOST	127.0.0.1	Bind host. Use 0.0.0.0 to accept connections from another machine on the LAN.
KV_DEMO_TOKEN	unset	Optional shared secret. When set, data and MCP routes require it.

When KV_DEMO_TOKEN is set, present it as Authorization: Bearer <token>. For the browser UI, open http://127.0.0.1:8848/#token=<token>; the fragment is not sent to the server and the page removes it from the address bar before polling /api/state with the bearer header. The token is a convenience guard for local demos, not a hardened auth scheme; do not expose this server to untrusted networks.

Connecting from Paperclip

The KV demo is meant for the remote_http connection path. The server speaks Streamable HTTP at /mcp, runs in a single process so the Values UI and the MCP tools share state, and listens on a fixed loopback port. Paperclip's remote-HTTP gateway proxies every call through policy and audit while leaving process supervision to you (just Ctrl+C the server when you are done).

Via the Connect-an-app wizard (recommended)

1. Open the company's Tools UI at /<prefix>/companies/<companyId>/tools.
2. Go to Connect an app and pick Connect with a link.
3. Paste http://127.0.0.1:8848/mcp and give it a name (e.g. "KV demo").
4. If you launched the server with KV_DEMO_TOKEN, paste the token in the App key field. The wizard stores it as an Authorization: Bearer … header secret.
5. Pick the profile defaults (read/write/destructive) and finish. Paperclip imports the four tools and quarantines kv_delete.

The wizard hits this API under the hood:

curl -fsS -X POST \
  -H "Authorization: Bearer $BOARD_API_KEY" \
  -H "Content-Type: application/json" \
  "$PAPERCLIP_URL/api/companies/$COMPANY_ID/tools/apps/connect" \
  -d '{
    "link": "http://127.0.0.1:8848/mcp",
    "name": "KV demo"
  }'

If a token is set, add the credentialValues block:

{
  "link": "http://127.0.0.1:8848/mcp",
  "name": "KV demo",
  "credentialValues": {
    "credentials.authorization": "my-demo-secret"
  }
}

Transport tradeoffs

• remote_http (recommended for this demo) — required if you want the Values UI to reflect what the agent just did. The KV demo intentionally holds state in one process and exposes both the MCP endpoint and the UI from that process. Paperclip's remote_http gateway forwards every call to the same loopback URL, so the UI always sees the same store the tools mutated.
• local_stdio (not used here) — runs MCP servers as supervised child processes inside Paperclip's runtime slots. Reserved for trusted local deployments (developer laptop, local_trusted or authenticated/private with PAPERCLIP_TRUSTED_MCP_RUNTIME_HOST set on a single trusted worker). Each runtime slot has its own process, which would give each slot its own in-memory store — you would lose the shared-state property that makes this demo work. Use the approved stdio templates that ship in the Paperclip build when you need stdio; do not try to shoehorn this server into a local-stdio template.

For the full transport policy across deployment modes, see MCP-ACCESS-GOVERNANCE.md → Local trusted deployment.

What you should see in Paperclip

After the wizard finishes, expect:

• Catalog — four tools imported from this connection. kv_list and kv_get are tagged read; kv_set is tagged write; kv_delete is tagged destructive and starts in quarantined status.
• Tools panel on an agent — kv_list, kv_get, and (with the default ask-first policy) kv_set. kv_delete is not listed until you take it out of quarantine.
• Audit feed — one row per call. Reads show tool_gateway.call_completed with decision: allow. Writes that hit the default ask-first policy show tool_gateway.approval_requested followed by tool_gateway.call_allowed and tool_gateway.call_completed once you approve. Calls to kv_delete show tool_gateway.call_denied with reasonCode: quarantined_catalog_entry.

The recorded walkthrough in doc/MCP-DEMO-SCRIPT.md runs all three cases end-to-end against this package and matches the audit rows above.

What lives where

Concern	Stored in this package	Stored in Paperclip
Key/value entries (kv_* data)	In-memory Map, lost on restart.	Not stored. Paperclip never sees the values directly; the gateway only sees the MCP request/response envelope and the redacted-by-policy view the audit log keeps.
Connection record (URL, token, transport)	Not stored.	Persisted in tool_connections. The optional token becomes a secret.
Profile / policy / binding decisions	Not stored.	Persisted under tool_profiles, tool_policies, and tool_profile_bindings.
Approval action requests	Not stored.	Persisted under tool_action_requests, linked to issue-thread interactions.
Audit rows for each call	Not stored.	Persisted under tool_call_events. Append-only.

Cleanup and reset

Resetting the demo state usually means resetting this process; Paperclip's records stay intact unless you also archive the connection.

• Empty the KV store — Ctrl+C (or kill) the server and start it again. The new process starts with zero keys and revision 0. There is no in-process reset endpoint by design; restart is the single supported reset.

• Free the port — if startup logs EADDRINUSE, another kv-demo process is still bound to 8848. Find and kill it:

  lsof -nP -iTCP:8848 -sTCP:LISTEN
  kill <pid>
  

• Quiesce the Paperclip side — disable the connection so the gateway stops trying to reach the now-stopped server:

  curl -fsS -X PATCH \
    -H "Authorization: Bearer $BOARD_API_KEY" \
    -H "Content-Type: application/json" \
    "$PAPERCLIP_URL/api/tool-connections/$CONNECTION_ID" \
    -d '{ "enabled": false, "status": "disabled" }'
  

• Archive the application when you are fully done. Audit history is retained, but no new calls can land:

  curl -fsS -X PATCH \
    -H "Authorization: Bearer $BOARD_API_KEY" \
    -H "Content-Type: application/json" \
    "$PAPERCLIP_URL/api/tool-applications/$APPLICATION_ID" \
    -d '{ "status": "archived" }'
  

The KV demo is a fixture, not a piece of infrastructure. Treat each session as disposable: start it, run the demo, kill it.