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Chase overdue invoices on a ladder anchored to the due date: reminder 1, reminder 2, the final notice, with the aging and the day's chase list. You register an unpaid invoice, client, reference, amount in whole minor units, currency, due date, and it returns a DUN-YYYY-NNNN id with the three escalation dates: reminder 1 at due plus 7 days, reminder 2 at due plus 14, the final notice at due plus 21, configurable per invoice. The ladder is anchored to the due date, not to the last letter, so a reminder that goes out twelve days late does not push the final notice back: the client's obligation was fixed by the due date. Letters go out strictly in order, and the late fee is simple interest, pro-rata on a 30-day month, on what is outstanding the day the letter is written, rounded once to the minor unit. letter_render produces the letter as Markdown or a self-contained printable HTML page, letter_sent records that it actually went out, and payment_record lowers what the next letter asks for, with a payment that covers the balance closing the ladder. Nothing is emailed or sent anywhere: the server produces the letter text, and sending it is your act.
The weekly chase is a Friday job done in this window: chase_today names what crosses a threshold today, letter_render produces the text, and you paste it into the mail yourself, because the server sends nothing anywhere. The record of what went out and when is then on the same machine the invoice book is on.
| You say | Tool |
|---|---|
| Register INV-1042 to Acme Ltd, USD 1,250.00, due 2026-06-01, late fees at 2% a month. | invoice_register |
| What do I need to send today? | chase_today |
| They paid 500 on the 20th; record it and show me the final notice when it falls due. | payment_record then letter_render |
On the worked chase, USD 125,000 minor units due 2026-06-01 with the default gaps falls due on 06-08, 06-15 and 06-22 whether or not anything was sent, and on 2026-07-01 the fee at 2% per month is exactly 2,500. After a 50,000 part payment the fee on the remainder is 1,500, so the final notice asks for 76,500 and no invented figure more. The unit suite recomputes every one of those by hand.
The file is claude_desktop_config.json, and the key inside it is mcpServers.
| Scope | Path |
|---|---|
| macOS | ~/Library/Application Support/Claude/claude_desktop_config.json |
| Windows | %APPDATA%\Claude\claude_desktop_config.json |
One click, no JSON. Download dunning-letters.mcpb from the
latest release and open it. Claude Desktop installs it as an extension and runs
it on the Node runtime it ships with, so neither your PATH nor your node version comes into it, and there
is no file to edit. Everything below is the manual route, for when you want the entry in the config file
itself.
The config block, which needs both strings absolute:
{
"mcpServers": {
"dunning-letters": {
"command": "node",
"args": ["/absolute/path/to/mcp-servers/servers/dunning-letters/dist/index.js"]
}
}
}If node came from nvm, asdf or homebrew, use the absolute path that which node prints
rather than the bare word, because a stdio server started by this app inherits a limited PATH:
"command": "/Users/you/.nvm/versions/node/v22.14.0/bin/node"The node command above wants a built file. From a clone, once:
git clone https://github.com/theluckystrike/mcp-servers.git
cd mcp-servers && npm install
npm run build -w packages/mcp-license -w servers/dunning-lettersThat writes servers/dunning-letters/dist/index.js, and its absolute path is the one argument
the config needs.
The npm packages are not published yet, so the form below returns a 404 today. It is here because it is what the entry becomes the day the publish lands, with nothing else changed:
{
"mcpServers": {
"dunning-letters": {
"command": "npx",
"args": ["-y", "@theluckystrike/mcp-dunning-letters"]
}
}
}Save, then completely quit Claude Desktop and start it again. A window reload is not enough.
Nothing is published to npm yet, so the working install paths are the ones above: the .mcpb bundle from the latest release, a clone and build, or the hosted URL.
There is no hosted endpoint for this one yet. MCP Dunning Letters runs locally over stdio with the config above, which is also the only form in which it reads and writes files on your own disk. Thirty of the servers in this collection are served at https://mcp.zovo.one/mcp/<name> over MCP streamable HTTP; https://mcp.zovo.one/mcp/connect lists them and prints a ready URL for each.
Two documented facts decide whether the entry works: every path in claude_desktop_config.json must be absolute, and a stdio server started here inherits only a limited, platform-dependent subset of environment variables. If node came from nvm or homebrew, paste what `which node` prints instead of the bare word. The .mcpb route avoids both: Claude Desktop ships a built-in Node.js environment.
Free: Three unpaid invoices chased at once, with all three letters in both formats, the aging summary, the day's chase list and payment recording free on every tier. An invoice that gets paid frees its slot, because the cap is on how many chases run at once, never on the letters or the aging. Pro is $19 once, verified offline.
macOS: ~/Library/Application Support/Claude/claude_desktop_config.json. Windows: %APPDATA%\Claude\claude_desktop_config.json. There is no published Linux path. Settings, Developer, Edit Config opens the right copy and creates it if it does not exist.
In order: did you fully quit and restart, not just close the window? Is every path absolute? And is the command resolvable, given the limited environment a stdio server inherits here? If node came from nvm, paste what which node prints.
Yes. An .mcpb bundle, the format renamed from .dxt, opens with Claude and shows an installation dialog. One you built yourself goes in through Settings, Extensions, Advanced settings, Install Extension.
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