fldigi-mcp

An MCP server for controlling fldigi, the popular amateur-radio digital-modem application, from MCP-aware clients such as Claude Desktop.

fldigi ships a built-in XML-RPC control interface. fldigi-mcp connects to it and exposes the whole API as a small set of logically-grouped MCP tools, so an assistant can read the radio's state and drive the modem, rig, log, and transmitter through plain language.

Status: beta. Full API coverage, callsign-gated transmit, and an optional experimental Band Guidance feature. Tested against fldigi 4.2.x.

📻 A field-tested fldigi XML-RPC API reference (free community resource)

Building this server meant mapping fldigi's entire XML-RPC interface and verifying every method against a live build — so we've written it all up and are sharing it freely, whether or not you ever use this MCP server:

• docs/FLDIGI-API.md — a clean, complete, human-readable reference organized by namespace, with transport details, types, worked examples, a transmit-safety section, and field-tested gotchas.
• docs/FLDIGI-API.pdf — the same, as a printable PDF.
• docs/FLDIGI-API-SPEC.md — a terse, machine-readable catalog of all 174 methods (args, return type, read/write/keying).

Verified live against fldigi 4.2.11 via fldigi.list. It's more complete and current than the public wiki (it documents methods the wiki omits, e.g. TxID, and flags deprecated ones). Independent project — not affiliated with the fldigi / W1HKJ project. Corrections welcome via issues / PRs.

Highlights

• Complete control — every documented XML-RPC method is reachable, grouped into ~14 tools (one permission each) plus a fldigi_call escape hatch for the long tail and future methods.
• Safe by default — the callsign is the single transmit gate. With no callsign configured the station is receive-only; nothing can key the radio.
• Names match fldigi — tools and operations mirror fldigi's own API namespaces and on-screen labels (Op Mode, AFC, SQL, Rev, Lock, RxID/TxID, T/R).
• No fragile dependencies — talks to fldigi with Python's standard-library xmlrpc.client. The only third-party runtime deps are the MCP SDK and PyYAML (for the optional band-plan data).

Why XML-RPC (and not a third-party library)

fldigi's XML-RPC interface is its official, OS-independent control API. This project talks to it directly rather than through an unmaintained wrapper, keeping the moving parts to Python's standard library and fldigi's own API.

Requirements

To install the desktop extension (.mcpb) all you need is:

• fldigi running (its XML-RPC server is on by default at 127.0.0.1:7362).

Claude Desktop's uv runtime supplies Python and the dependencies, so end users do not install Python or uv themselves. (That runtime is currently marked experimental, so a recent Claude Desktop is recommended.)

For development from source you additionally need Python 3.10+ and uv (and Node.js, only for the MCP Inspector).

Install

Easiest: one-click desktop extension

Download fldigi-mcp.mcpb from the latest release, then in Claude Desktop go to Settings → Extensions → Advanced settings → Install Extension… and choose the file. A short settings form asks for your callsign (everything else has a default). No terminal, no Python, no uv to install.

👉 New to this? Follow the simple step-by-step install guide. Also see the install & safety model.

From source (development)