NATS

from daanrongen

MCP server for NATS — publish, request-reply, JetStream streams, KV store, and server diagnostics over stdio

🔥🔥🔥🔥✓ VerifiedFreeQuick setup

⌁ labsco summary — our analysis, not the vendor's

What it is — An MCP server for NATS that publishes messages, does request-reply, manages JetStream streams, uses the KV store, and inspects server diagnostics over stdio.

What you get —

Core — publish and request (request-reply pattern)
JetStream — stream_create/list/info/delete, stream_publish, stream_fetch, stream_consumer_create
KV store — kv_create_bucket, kv_get/put/delete, kv_list_keys, kv_history
Server — server_info diagnostics
17 tools total

Requirements — A running NATS server URL (NATS_URL, e.g. nats://localhost:4222), required.

Cost snapshot — Free; license not stated in the README. NATS itself is open source and self-hosted.

Setup effort — bunx @daanrongen/nats-mcp, or claude mcp add nats -e NATS_URL=... -- bunx @daanrongen/nats-mcp.

Our take — A capable bridge for teams already running NATS/JetStream who want to inspect and drive messaging from an assistant. Caveat: it assumes a reachable NATS server (no auth options shown beyond the URL), and the license is unspecified — confirm before commercial use.

Source: the project README — summarized 2026-07-08.

⌁ readme from github — mirrored (latest on GitHub ↗)

nats-mcp

MCP server for NATS — publish messages, request-reply, manage JetStream streams, use the KV store, and inspect server diagnostics over stdio.

Tools (17 total)

Domain	Tools	Coverage
Core	`publish`, `request`	Publish messages, request-reply pattern
Streams	`stream_list`, `stream_info`, `stream_create`, `stream_delete`, `stream_publish`, `stream_fetch`, `stream_consumer_create`	JetStream stream lifecycle and message delivery
KV	`kv_create_bucket`, `kv_list_buckets`, `kv_get`, `kv_put`, `kv_delete`, `kv_list_keys`, `kv_history`	Key-value store with history
Server	`server_info`	NATS server diagnostics

Development

bun install
bun run dev        # run with --watch
bun test           # run test suite
bun run lint       # lint and check formatting
bun run typecheck  # type check
bun run build      # bundle to dist/main.js
bun run inspect    # open MCP Inspector in browser

Inspecting locally

bun run inspect launches the MCP Inspector against the local build:

bun run build && bun run inspect

This opens the Inspector UI in your browser where you can call any tool interactively and inspect request/response shapes.

Architecture

src/
├── config.ts              # Effect Config — NATS_URL
├── main.ts                # Entry point — ManagedRuntime + StdioServerTransport
├── domain/
│   ├── NatsClient.ts      # Context.Tag service interface
│   ├── errors.ts          # NatsError, KvNotFoundError, StreamNotFoundError
│   └── models.ts          # Schema.Class models (NatsMessage, StreamInfo, KvEntry, …)
├── infra/
│   ├── NatsClientLive.ts  # Layer.scoped — connects via nats.js, drains on shutdown
│   └── NatsClientTest.ts  # In-memory Ref-based test adapter
└── mcp/
    ├── server.ts          # McpServer wired to ManagedRuntime
    ├── utils.ts           # formatSuccess, formatError
    └── tools/             # core.ts, streams.ts, kv.ts, server.ts

Copy & paste — that's it

{
  "mcpServers": {
    "nats": {
      "type": "stdio",
      "command": "bunx",
      "args": ["@daanrongen/nats-mcp"],
      "env": {
        "NATS_URL": "nats://localhost:4222"
      }
    }
  }
}

Before it works, you'll need: NATS_URL

Installation

bunx @daanrongen/nats-mcp

Configuration

Variable	Required	Description
`NATS_URL`	Yes	NATS server URL (e.g. `nats://localhost:4222`)

Setup

Claude Desktop

Edit ~/Library/Application Support/Claude/claude_desktop_config.json:

{
  "mcpServers": {
    "nats": {
      "type": "stdio",
      "command": "bunx",
      "args": ["@daanrongen/nats-mcp"],
      "env": {
        "NATS_URL": "nats://localhost:4222"
      }
    }
  }
}

Claude Code CLI

claude mcp add nats -e NATS_URL=nats://localhost:4222 -- bunx @daanrongen/nats-mcp