bookmark-mcp
Click on "Install Server".
Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state.
In the chat, type
@followed by the MCP server name and your instructions, e.g., "@bookmark-mcpsave https://example.com with tag testing"
That's it! The server will respond to your query, and you can continue using it as needed.
Here is a step-by-step guide with screenshots.
bookmark-mcp — a production-ready MCP server showcase
A deliberately simple business case (a personal bookmark / reading-list manager) implemented the current standard way to build a Model Context Protocol server, so you can focus entirely on the technology:
TypeScript + the official
@modelcontextprotocol/sdk(high-levelMcpServerAPI)All three MCP primitives: tools, resources (static + templates), prompts
Local dev & testing on stdio / Node HTTP — production on Cloudflare Workers (Durable Object storage, deployed with one command)
Zod schemas as the single source of truth for validation, TypeScript types, and the JSON Schema shown to clients
Structured tool output (
outputSchema+structuredContent) and tool annotations (readOnlyHint,destructiveHint, …)Production patterns: pluggable storage adapters, stderr-only logging, atomic file writes, in-band error handling, origin validation, graceful shutdown, health endpoint
End-to-end tests with a real MCP client over the SDK's in-memory transport
src/
├── index.ts # entrypoint: stdio transport (local use with Claude Code/Desktop)
├── http.ts # entrypoint: Node Streamable HTTP (local/self-hosted, session-managed)
├── worker.ts # entrypoint: Cloudflare Worker + Durable Object ← PRODUCTION
├── server.ts # MCP layer: registers tools, resources, prompts (transport-agnostic)
├── store.ts # domain layer: BookmarkStore (runtime-agnostic, no node:* imports)
├── storage/
│ ├── file.ts # StorageAdapter: JSON file with atomic writes (Node only)
│ └── memory.ts # StorageAdapter: in-memory (tests)
├── schemas.ts # Zod schemas: validation + types + JSON Schema, all from one place
├── config.ts # env-var configuration (Node entrypoints)
├── logger.ts # structured logger (stderr on Node, log stream on Workers)
├── server.test.ts # end-to-end protocol tests (client ↔ server, in-memory)
└── store.test.ts # domain unit tests
wrangler.jsonc # Cloudflare deployment config (DO binding + migration)Why a bookmark manager?
The use case fits in one sentence — "save URLs, find them again, mark them read" — so every line of code is about how to build an MCP server, not about understanding a domain. Yet it is rich enough to exercise everything: create/read/update/delete actions, search filters, derived data (tag stats), duplicates and not-found errors, and persistence.
Related MCP server: Library MCP
Quick start
npm install
npm test # 15 end-to-end + unit tests
npm run dev # run on stdio (for MCP clients)
npm run dev:http # Node server on http://127.0.0.1:3000/mcp
npm run dev:worker # the PRODUCTION worker, locally in workerd (http://localhost:8787/mcp)
npm run inspect # open the MCP Inspector UI against this server
npm run deploy # ship to Cloudflare Workers (needs `npx wrangler login` once)Connect it to Claude Code
claude mcp add bookmarks -- npx tsx /absolute/path/to/playground_mcp/src/index.tsConnect it to Claude Desktop
{
"mcpServers": {
"bookmarks": {
"command": "npx",
"args": ["tsx", "/absolute/path/to/playground_mcp/src/index.ts"],
"env": { "BOOKMARKS_FILE": "/Users/you/bookmarks.json" }
}
}
}Then ask things like "bookmark https://example.com/article with tag testing", "what's unread in my reading list?", or invoke the reading_digest prompt.
Configuration
Env var | Default | Used by |
|
| both transports |
|
| both ( |
|
| HTTP only |
|
| HTTP only |
Architecture
Two design decisions make the "test locally, run on Cloudflare" split cheap:
The MCP layer is transport-agnostic.
createServer()builds the same server whether it is served over stdio, Node HTTP, the Workers transport, or an in-memory pipe in tests.The domain layer is runtime-agnostic.
store.tsuses only Web-standard APIs (nonode:*imports) and persists through a 2-methodStorageAdapterport. The file adapter is for laptops; the Durable Object adapter is production; the memory adapter is for tests.
flowchart LR
subgraph Clients
CD["Claude Desktop / Claude Code"]
IN["MCP Inspector"]
T["Vitest test client"]
end
subgraph Entrypoints
STDIO["index.ts<br/>stdio (local dev)"]
HTTP["http.ts<br/>Node Streamable HTTP"]
CF["worker.ts<br/>Cloudflare Worker + DO (production)"]
MEM["InMemoryTransport<br/>(tests)"]
end
subgraph Server["server.ts — createServer()"]
TOOLS["Tools<br/>add_bookmark · search_bookmarks<br/>mark_read · delete_bookmark"]
RES["Resources<br/>bookmarks://all · bookmarks://stats<br/>bookmarks://bookmark/{id}"]
PROMPTS["Prompts<br/>reading_digest"]
end
subgraph Domain["store.ts — BookmarkStore (runtime-agnostic)"]
STORE["StorageAdapter port"]
end
FILE[("storage/file.ts<br/>bookmarks.json, atomic writes")]
DO[("Durable Object storage<br/>strongly consistent")]
RAM[("storage/memory.ts")]
CD --> STDIO
IN --> STDIO
CD -.->|"remote: workers.dev/mcp"| CF
T --> MEM
STDIO --> Server
HTTP --> Server
CF --> Server
MEM --> Server
TOOLS --> Domain
RES --> Domain
PROMPTS --> Domain
STORE --> FILE
STORE --> DO
STORE --> RAMThe three MCP primitives — who controls what
Primitive | Controlled by | This server | Typical UI |
Tools | the model — the LLM decides when to call them |
| tool-use with permission prompt |
Resources | the application — the client attaches them as context |
| "attach context" picker |
Prompts | the user — explicitly invoked |
| slash command / menu |
Flows
1. Connection lifecycle (initialize handshake)
Every MCP session, on any transport, starts with the same three-step handshake in which client and server negotiate protocol version and capabilities:
sequenceDiagram
participant C as Client (Claude)
participant S as bookmark-mcp
C->>S: initialize (protocolVersion, capabilities, clientInfo)
S-->>C: result (serverInfo, capabilities: tools/resources/prompts, instructions)
C->>S: notifications/initialized
Note over C,S: Session is live
C->>S: tools/list
S-->>C: 4 tools with JSON Schemas + annotations
C->>S: resources/list · prompts/list
S-->>C: resource & prompt catalogs
Note over C,S: ... normal operation (see flow 2) ...
C->>S: close / SIGTERM
S->>S: flush write queue, close transport2. Tool call flow (what happens on "bookmark this URL")
sequenceDiagram
actor U as User
participant L as LLM
participant C as MCP Client
participant S as server.ts
participant D as store.ts
U->>L: "Save https://ex.com/post with tag rust"
L->>C: tool_use: add_bookmark {url, tags:["rust"]}
C->>S: tools/call add_bookmark
S->>S: Zod validates input against schema
alt input invalid
S-->>C: result { isError: true, "Invalid URL ..." }
Note over L: LLM reads the error and self-corrects
else input valid
S->>D: store.add(...)
alt duplicate URL
D-->>S: DuplicateUrlError
S-->>C: result { isError: true, "already bookmarked (id ...)" }
else success
D->>D: atomic write: tmp file + rename
D-->>S: Bookmark
S-->>C: result { content: [text], structuredContent: {bookmark} }
end
end
C->>L: tool result
L->>U: "Saved! It's in your reading list under 'rust'."Two error channels, used deliberately:
In-band tool errors (
isError: true) for expected business failures — duplicates, not-found, invalid input. The LLM sees the message and can recover (e.g. search for the existing bookmark instead).Protocol errors (JSON-RPC errors / thrown exceptions) only for unexpected bugs.
3. Streamable HTTP session lifecycle (Node self-hosted variant)
The stdio transport is one process per client — no session management needed. The Node remote server uses Streamable HTTP with explicit sessions:
sequenceDiagram
participant C as Remote client
participant H as http.ts (node:http)
participant T as StreamableHTTPServerTransport
participant S as McpServer (per session)
C->>H: POST /mcp (initialize, no session header)
H->>H: validate Origin header (DNS-rebinding defense)
H->>T: new transport + sessionIdGenerator()
H->>S: createServer(store).connect(transport)
T-->>C: 200 + Mcp-Session-Id: <uuid>
C->>H: POST /mcp (Mcp-Session-Id: <uuid>) — tools/call etc.
H->>T: route to session's transport
T-->>C: response (JSON or SSE stream)
C->>H: GET /mcp (Mcp-Session-Id) — optional
T-->>C: SSE stream for server→client notifications
C->>H: DELETE /mcp (Mcp-Session-Id)
T->>H: onsessionclosed → remove from session mapAll sessions share one BookmarkStore, so the data is consistent across clients; each session gets its own McpServer instance, so protocol state never leaks between clients.
4. Persistence: why writes can't corrupt the data
Locally (FileStorage adapter):
flowchart TD
A["tool handler mutates Map"] --> B["persist() appends to write queue"]
B --> C{previous write done?}
C -- "no" --> W["wait (serialized writes)"] --> D
C -- "yes" --> D["write bookmarks.json.PID.tmp"]
D --> E["rename() over bookmarks.json — atomic on POSIX"]
E --> F["crash at any point ⇒ old file intact"]In production the Durable Object gives the same guarantees for free: its storage API is transactional, and the DO is single-threaded so writes are serialized by the platform itself.
Production: Cloudflare Workers
worker.ts is the production entrypoint. The stateless Worker routes every request to one named Durable Object instance, which owns the data and runs the MCP server:
sequenceDiagram
participant C as MCP client (Claude)
participant W as Worker (edge, stateless)
participant D as Durable Object "default"
participant S as DO storage (SQLite-backed)
C->>W: POST https://bookmark-mcp.you.workers.dev/mcp
W->>D: idFromName("default") → stub.fetch(request)
Note over D: first request after cold start?
D->>S: read + Zod-validate persisted store
D->>D: fresh McpServer + WebStandard transport<br/>(stateless: no Mcp-Session-Id)
D->>S: transactional write on mutation
D-->>C: JSON-RPC response (plain JSON)Why this shape:
Stateless MCP (
sessionIdGenerator: undefined,enableJsonResponse: true): serverless requests may hit any isolate, so there are no sticky sessions to manage — each POST is self-contained. This is the recommended pattern for serverless MCP hosting.One DO = the consistency boundary. DO storage is strongly consistent and the instance is single-threaded, so concurrent clients can't corrupt data — the platform replaces both the atomic file writes and the write queue we need locally.
McpAgentalternative: Cloudflare'sagentsframework is the batteries-included route (per-session DOs, hibernation, OAuth templates). It needs external shared storage (KV/D1) because each session gets its own DO; the single shared DO here keeps the showcase self-contained and dependency-light. Reach forMcpAgentwhen you need server→client notifications or the OAuth flow.Multi-tenancy is one line away: derive the DO name from the authenticated user (
idFromName(userId)) and every user gets an isolated store.
Deploy
npx wrangler login # once
npm run deploy # builds + ships; prints https://bookmark-mcp.<you>.workers.devConnect Claude to the deployed server:
claude mcp add --transport http bookmarks https://bookmark-mcp.<you>.workers.dev/mcpLocal test of the exact production code path (runs in workerd, with a local DO):
npm run dev:worker # http://localhost:8787/mcp + /healthzBefore sharing the URL publicly, add auth — simplest is Cloudflare Access in front of the route; the full-fidelity option is the MCP OAuth 2.1 flow (workers-oauth-provider). The free plan (100k requests/day, SQLite-backed DOs included) comfortably covers personal use.
Production patterns demonstrated
Concern | Where | Pattern |
stdout discipline | On stdio, stdout is the protocol. One stray | |
Validation at the boundary | Zod raw shapes with | |
Structured output | Tools declare | |
Tool annotations |
| |
Recoverable errors | Business failures are | |
Pluggable storage | Runtime-agnostic domain layer + 2-method | |
Durable writes | Locally: temp-file + | |
Remote security | Origin validation, | |
Graceful shutdown | both entrypoints | SIGINT/SIGTERM close sessions and the transport before exiting. |
Testing | A real | |
Config via env | Matches how MCP clients pass configuration ( |
Production checklist (what's still missing before a public launch)
The Workers deployment already covers TLS, scaling, durable storage, and observability (wrangler tail / dashboard logs). What this showcase deliberately leaves out:
Authentication — the MCP spec mandates OAuth 2.1 for remote servers. On Cloudflare:
workers-oauth-provider(full spec flow) or Cloudflare Access with a service token (pragmatic personal setup). On Node:@modelcontextprotocol/sdk/server/authhelpers.Multi-tenancy — currently all clients share one bookmark collection; derive the DO name from the authenticated user to isolate stores.
Rate limiting & request size caps — Cloudflare WAF rules or a rate-limit binding.
Server→client notifications — the stateless Worker pattern has no SSE channel; if you need
listChangednotifications or progress streams, move to session-managed transports (Nodehttp.tsalready does this; on Workers useMcpAgent).
Extending the server
Adding a capability is a three-step pattern — schema, domain, registration:
Define the input shape in schemas.ts with
.describe()on every field.Add the operation to store.ts (plus a typed error class if it can fail in an expected way).
Register it in server.ts with
registerTool/registerResource/registerPrompt, and add a case to server.test.ts.
Debugging
npm run inspect # MCP Inspector: interactive UI for tools/resources/prompts
LOG_LEVEL=debug npm run dev # verbose stderr logs (Node)
npm test # full protocol round-trip without any client
npm run dev:worker # production code path locally (workerd + local DO)
npx wrangler tail # live logs from the deployed WorkerThis server cannot be installed
Maintenance
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