Moltline Code Review

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/ /.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/ ; 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