moltline-mcp

A thin, dependency-free stdio bridge to Moltline Studio's fleet of 14 hosted MCP servers.

Most modern MCP clients can connect to the fleet directly over Streamable HTTP — no install needed (see Direct connection below). This bridge exists for clients that only speak the stdio transport: it proxies newline-delimited JSON-RPC between your client and the hosted server, verbatim, with no telemetry and no dependencies beyond the Python 3.9+ standard library.

• Free tier: no registration, no account, no credentials — connect and call tools immediately.

• Premium tools are unlocked with a Moltline license, presented only as a tool argument (never in URLs or headers). See auth.md.

• Fleet is independently audited: MCPize Verified A on direct endpoints.

The fleet

Machine-readable discovery: api-catalog · per-server card at https://mcp.moltlinestudio.com/<server>/.well-known/mcp/server-card.json · fleet health.

Related MCP server: proxy-mcp

Direct connection (preferred)

If your MCP client supports Streamable HTTP (Claude Desktop, Claude Code, Cursor, and most current clients do), point it straight at the hosted endpoint — nothing to install:

{
  "mcpServers": {
    "moltline-timeops": {
      "type": "http",
      "url": "https://mcp.moltlinestudio.com/timeops"
    }
  }
}

Swap timeops for any slug in the table above.

The stdio bridge (for stdio-only clients)

Install

pip install moltline-mcp        # from PyPI, or:
pipx install moltline-mcp       # isolated install

Or run it straight from a checkout — it is a single stdlib-only file:

python3 moltline_mcp.py timeops

Client configuration

{
  "mcpServers": {
    "moltline-timeops": {
      "command": "moltline-mcp",
      "args": ["timeops"]
    }
  }
}

CLI

moltline-mcp [server] [--timeout SECONDS] [--list] [--version]

• server — one of the 14 slugs (default catalog); anything else fails fast with the valid list.

• --timeout — per-request timeout in seconds (default 300, or env MOLTLINE_TIMEOUT).

• --list — print the server slugs and exit.

• Env MOLTLINE_BASE_URL — override the fleet base URL (for testing).

• Env MOLTLINE_DEBUG=1 — diagnostic logging on stderr (stdout stays protocol-clean).

Docker

The bridge also runs containerized (stdio in, network egress to the fleet required):

docker build -t moltline-mcp .
docker run -i --rm moltline-mcp timeops   # any of the 14 slugs; default: catalog

Point your MCP client's command at docker with args ["run", "-i", "--rm", "moltline-mcp", "timeops"].

How it works

One process per server connection. Each JSON-RPC message read from stdin is POSTed to https://mcp.moltlinestudio.com/<server>; JSON and SSE-framed responses are relayed back to stdout as newline-delimited JSON. The bridge tracks the server-assigned Mcp-Session-Id and echoes the negotiated MCP-Protocol-Version, per the Streamable HTTP transport spec. It never inspects, stores, or reports your traffic.

Access and licensing

• Free tier — anonymous. No registration or credentials; all free tools work immediately.

• Premium — unlocked with a Moltline license purchased (human-in-the-loop) at moltlinestudio.com. The license is passed as a tool argument where a premium tool asks for it — never as a bearer header, never in URLs. Details: auth.md.

Links

• Website: https://moltlinestudio.com

• Agent access guide: https://moltlinestudio.com/auth.md

• API catalog: https://moltlinestudio.com/.well-known/api-catalog

• Community: https://community.moltlinestudio.com

• Issues and security reports: see SECURITY.md

License

MIT © 2026 Moltline Studio