moltline-mcp

A thin, dependency-free stdio bridge to Moltline Studio's fleet of 22 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.

• 160 tools across 22 servers; 110 are free.
• Free tier: no registration, no account, no credentials — connect and call tools immediately.
• Premium tools are unlocked with a Moltline license. Set MOLTLINE_LICENSE in your MCP client's environment; the bridge sends it as the X-Moltline-License header and never writes it to argv, URLs or logs. See auth.md.
• Independently checked by MCPize on the direct endpoints (scans of 5–6 September 2026: 6 A+, 15 A, 1 B+; scores 89–98). All 22 servers score 100 on clarity, 100 on reliability and 100 on trust, 95 on protocol and 87 on safety; the one finding raised on every server is that the free tier accepts anonymous access — which is the point of it — and the spread between servers sits in MCPize's "Market" dimension (a crowded category). Each server's MCPize listing links its own public result.

Find it on: Smithery · MCPize · Glama · Clawmart · MCP Registry

The fleet

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

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

Run directly (recommended) — the bridge is a single stdlib-only file, so a clone is all you need:

git clone https://github.com/GarphenGate/moltline-mcp.git
python3 moltline-mcp/moltline_mcp.py timeops   # any of the 22 slugs; default: catalog

Docker — see Docker below if you prefer a container.

A PyPI package is planned; until then, use the methods above.

Client configuration

Point your MCP client at the script with an absolute path:

{
  "mcpServers": {
    "moltline-timeops": {
      "command": "python3",
      "args": ["/absolute/path/to/moltline-mcp/moltline_mcp.py", "timeops"]
    }
  }
}

Or run it through Docker (after docker build -t moltline-mcp .):

{
  "mcpServers": {
    "moltline-timeops": {
      "command": "docker",
      "args": ["run", "-i", "--rm", "moltline-mcp", "timeops"]
    }
  }
}

CLI

python3 moltline_mcp.py [server] [--timeout SECONDS] [--list] [--version]

• server — one of the 22 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_LICENSE — your Moltline license, sent as the X-Moltline-License header to unlock premium tools. Omit it and the bridge runs free-tier only.
• Env MOLTLINE_DEBUG=1 — diagnostic logging on stderr (stdout stays protocol-clean). The license is never logged; debug output reports only whether one is configured.

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 22 slugs; default: catalog

See Client configuration for the matching mcpServers entry.

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.

Tests

The bridge ships with an offline test suite - no network, no dependencies:

python -m unittest -v

Twenty-two tests cover the parts that actually break in a transport bridge: newline-delimited framing, SSE event splitting (multiple events, multi-line data: payloads, a trailing event with no blank line, comments and named events), session-id capture and reuse, protocol-version negotiation on initialize only, and error relay - a JSON-RPC error document is passed through verbatim, anything else becomes a well-formed -32603. CI runs them on Python 3.9, 3.12 and 3.13, plus a Docker build and container smoke test.

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. Set MOLTLINE_LICENSE in the environment and the bridge forwards it as the X-Moltline-License request header. It is deliberately not a command-line flag: argv is world-readable through ps. It is never placed in a URL and never logged. 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
• Agent protocol reference (x402, AP2, ACP, UCP, MPP, A2A): https://moltlinestudio.com/protocols.html
• Community: https://community.moltlinestudio.com
• Issues and security reports: see SECURITY.md

License

MIT © 2026 Moltline Studio