The full upstream README, mirrored here for reference. Install config, tool schemas, adoption signals, and an original overview live on the Contest MCP listing page.
An MCP server for logging amateur-radio QSOs to N3FJP logging software — Amateur Contact Log and the 100-plus N3FJP contest loggers — from MCP-aware clients such as Claude Desktop.
Every program in the N3FJP suite shares one TCP control API. n3fjp-mcp speaks
that protocol directly (Python's standard-library socket, no third-party
wrapper) and exposes it as a small set of logically-grouped MCP tools, so an
assistant can log contacts, read the log, run dupe checks, and manage band/mode
through plain language.
It is the logging half of an "operate → log" workflow; its sibling project
fldigi-mcp operates the radio.
Status: experimental (v0.3). Verified live against N3FJP's ARRL Field Day Contest Log, API version 2.2. The protocol is shared across the suite, but field sets vary per contest — confirm with the
fieldstool.
⚠️ Independent project — not affiliated with N3FJP
n3fjp-mcpis an independent, community project by Stefan Brunner (AE5VG), using the "N3FJP" name with the permission of its owner. It is not affiliated with, endorsed by, or supported by N3FJP Software / Affirmatech. Please direct all support questions for this app to its issue tracker — not to N3FJP. MIT licensed. "N3FJP" is the callsign and trademark of its owner.
log tool runs the real N3FJP flow:
set the call → CALLTAB (dupe check + previous-contact lookup) → set the
exchange → ENTER, surfacing the dupe response and the number of records added.n3fjp_call escape hatch for the long tail and future commands.confirm=true.N3FJP_ALLOW_DB_WIPE switch.ENTER, CALLTAB, the TXTENTRY… boxes, Class/Section, etc.).To install the desktop extension (.mcpb):
1100).Claude Desktop's uv runtime supplies Python and the dependencies, so end users
do not install Python or uv themselves.
For development from source you additionally need Python 3.10+ and uv (and Node.js, only for the MCP Inspector).
Download n3fjp-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 the host/port (defaults to
127.0.0.1:1100). No terminal, no Python, no uv to install.
👉 New to this? Follow the step-by-step install guide.
Then add it to Claude Desktop's config
(~/Library/Application Support/Claude/claude_desktop_config.json on macOS):
Restart Claude Desktop and ask "What's the N3FJP status?".
Each tool is one permission and takes an operation argument.
| Tool | Default | Controls |
|---|---|---|
status | read | snapshot: program, version, API version, QSO count, band/mode/frequency |
query | read | program, qso_count, next_serial, log/settings/shared paths, qso_rate, band_mode_freq |
fields | read | read one entry box, or list visible / all fields with values |
search | read | list recent, search, dupecheck (no side effects), entity status |
log | approval | log_qso (set call → CALLTAB → exchange → ENTER), set, set_many, calltab, enter, clear, focus |
bandmode | approval | change_freq, set_band, set_mode, ignore_rig_polls |
notifications | approval | enable / disable push events, drain buffered events |
database | approval | add_direct, delete a record, raw sql, checklog, openlog, sqlclose |
n3fjp_call | approval | escape hatch — send any raw command, incl. future ones |
All write tools sit at the Needs Approval tier, so you can set them to Always Allow in the client for hands-off automation. The single exception is a whole-database wipe (see below), which is hard-blocked regardless.
The headline is log → log_qso:
This sets the call, fires CALLTAB (dupe check), fills the exchange, sends
ENTER, and reports records added plus any dupe detail.
| Variable | Default | Purpose |
|---|---|---|
N3FJP_HOST | 127.0.0.1 | N3FJP API host |
N3FJP_PORT | 1100 | N3FJP API port (the suite's default) |
N3FJP_TIMEOUT | 6 | Socket/response timeout, seconds |
N3FJP_ALLOW_DB_WIPE | off | Danger. Allow whole-database delete/overwrite (raw SQL DROP/TRUNCATE/unscoped DELETE/UPDATE). Leave off unless you really mean it |
In the packaged desktop extension these appear as a settings form.
Logging doesn't key a transmitter, so there is no transmit gate. The protection here is about your log database:
status, query, fields, search) are marked
read-only — clients can default them to Always Allow.log), band/mode (bandmode),
notifications, and adding, editing, or deleting individual records
(database), plus the n3fjp_call escape hatch — all sit at the Needs
Approval tier. There is no extra in-band confirmation, so you can set them to
Always Allow in the client and let automation run hands-off.DROP, TRUNCATE, a DELETE/UPDATE with no WHERE) — are the
one exception: refused unless N3FJP_ALLOW_DB_WIPE is on. This switch is
separate from, and stricter than, the client's approval prompts, and carries a
stern warning in the settings form. Back up your log before ever enabling
it.Wherever possible, n3fjp-mcp leans on N3FJP's own validation (it dupe-checks
and reports oddities) and surfaces those responses rather than re-implementing
them.
If N3FJP runs on the same computer as Claude Desktop (the common case), leave
N3FJP_HOST at 127.0.0.1 and you're done.
If N3FJP runs on a different computer, there's a catch: a sandboxed MCP
client (notably Claude Desktop) runs the connector so it can only reach
127.0.0.1, not LAN addresses — so putting N3FJP's LAN IP in the settings will
time out even though telnet to that IP works. Fix it with the standalone
mcp-host-bridge tool on the
client computer, then set the host to 127.0.0.1:
Manage it with mcp-host-bridge status n3fjp / uninstall n3fjp. Full details
are in docs/REMOTE-HOST.md and the
mcp-host-bridge README.
The diagnostics tool helps confirm whether you need it. Keep the link on a
trusted LAN — the API is unauthenticated.
Building this server meant reverse-engineering and live-verifying the N3FJP TCP API, including several places where today's API (v2.2) differs from the public 0.9 documentation. We've written that up as a complete, human-readable guide and are sharing it freely to give back to the community:
CMD_NOT_FOUND, commands
removed since 0.9, the CALLTABEVENT lookup, and why ENTER can report 0 yet
still log in networked mode).Corrections and additions are welcome — please open an issue or PR.
The skills/ directory contains agent skills — operating
procedures distilled from live on-air use — bundled with the repo and the
.mcpb package:
The Operating Skills Field Guide
(PDF) documents this skill and its companion fldigi-operating from the
sibling fldigi-mcp — skills at
a glance, installation, a plain-language "first session" chapter for hams
new to Claude, the operating standard, the special-case playbook, and worked
examples transcribed from ARRL Field Day 2026.
To use with Claude Code / Cowork, copy the skill directory into your
~/.claude/skills/ (or a project's .claude/skills/). Pair it with the
fldigi-operating skill from fldigi-mcp for radio control.
The test suite covers the wire protocol, the operation maps and field catalog, type coercion, and the permission/confirm safety model; none of it requires a running N3FJP.
MIT © 2026 Stefan Brunner (AE5VG)