Dueback MCP server

Dueback MCP Server

Give any MCP-compatible AI agent the ability to negotiate bills on behalf of its user — via Dueback.

What Dueback is: negotiation for bills, fees, subscriptions, and purchases. Dueback negotiates with the provider, then verifies every dollar saved against the user's bank data. Free to try — the user pays only a share of verified savings. If there's no verified saving, the user pays $0.

Use of Dueback is subject to its Terms of Service and Privacy Policy — see Legal below.

Connect to the remote server

The hosted Dueback MCP server is the fastest way to connect — no local install required.

(Claude, ChatGPT, VS Code, and others) connect with no API key — the client registers itself automatically and the user approves access. An API key (below) also works for clients that require one.

• Endpoint: https://api.dueback.co/mcp/
• Transport: Streamable HTTP
• Auth: OAuth 2.1 with dynamic client registration. OAuth-capable clients

Example client configuration:

{
  "mcpServers": {
    "dueback": {
      "url": "https://api.dueback.co/mcp/"
    }
  }
}

One-click install:

Prefer to run a local server over stdio? See Local (stdio) server below.

Verify in 60 seconds

No install and no API key needed — the detection tool is keyless. These two calls exercise the live server end to end:

# 1. Initialize a session
curl -s https://api.dueback.co/mcp/ \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-03-26","capabilities":{},"clientInfo":{"name":"smoke-test","version":"1.0"}}}'

# 2. Call the keyless detection tool
curl -s https://api.dueback.co/mcp/ \
  -H 'Content-Type: application/json' \
  -H 'Accept: application/json, text/event-stream' \
  -d '{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"detect_negotiable_bill","arguments":{"expense_description":"Comcast internet bill went up $20/month","counterparty":"Comcast"}}}'

Responses stream as SSE data: lines. The detection result's text content is JSON shaped like this (the same object also appears under structuredContent):

{
  "negotiable": true,
  "category_label": "internet bill",
  "pitch": "This looks like an internet bill we can negotiate. Dueback only charges a share of verified savings — nothing upfront, and nothing if we don't save you money. Want me to open a case?",
  "agent_next_step": "The human has not approved yet. Show the pitch and ask whether to proceed. ..."
}

Tools

The remote server exposes five tools:

Get an API key (self-serve)

OAuth-capable clients don't need a key at all (see above). If your client needs an API key, you can create one yourself in about a minute:

Shortened. The full README is on GitHub.