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.
Eleven tools against Cascade's ceiling of 100, and it pairs naturally with mcp-invoice, whose overdue_report sees the same late payers, and mcp-statement-of-account, whose aging buckets the same book; budget the three at roughly 35 tools when you decide what else fits alongside them.
| 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 mcp_config.json, and the key inside it is mcpServers.
| Scope | Path |
|---|---|
| macOS, Windows and Linux | ~/.codeium/windsurf/mcp_config.json |
If you also run Claude Desktop, the shortest path there is one click: dunning-letters.mcpb
from the latest release opens as an extension, with no JSON and no terminal.
Windsurf reads its own config, so here it is:
The config block:
{
"mcpServers": {
"dunning-letters": {
"command": "node",
"args": ["/absolute/path/to/mcp-servers/servers/dunning-letters/dist/index.js"]
}
}
}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 and reopen the MCP Servers list; Cascade picks it up without restarting the editor.
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.
Read this first: mcp_config.json applies to the legacy Cascade agent only. The Devin Local agent, the default for new tabs, takes its servers from the Devin CLI config files, so a correct entry here can still be invisible in a fresh tab. The other hard number is a cap: Cascade reaches at most 100 tools at once, and every enabled server spends from it.
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.
~/.codeium/windsurf/mcp_config.json, under mcpServers. Reach it from the MCPs icon at the top right of the Cascade panel, or Devin Settings, Cascade, MCP Servers.
That file applies to the legacy Cascade agent only. The Devin Local agent, the default for new tabs, reads its servers from the Devin CLI config files instead. Check which agent the tab runs.
Cascade reaches at most 100 tools at any one time, and every enabled server spends from that single budget. MCP Dunning Letters contributes 11 tools, so keep the enabled list short rather than counting servers.
MCP Dunning Letters in detail · The same server in VS Code and Cline · Every server in Windsurf · Guides · Windsurf docs · Buy Pro