cbl-mcp-server/
├── src/
│   ├── server.cbl           # Main entry point and request loop
│   ├── transport.cbl        # I/O handling (read request, write response)
│   ├── parser.cbl           # JSON-RPC request parsing
│   ├── dispatcher.cbl       # Method routing
│   ├── response-builder.cbl # JSON-RPC response builders
│   └── tax-service.cbl      # Tax calculation logic
├── copybooks/
│   ├── CONSTANTS.cpy        # Protocol version constant
│   ├── STATUS.cpy           # Status flags (EOF, parsed)
│   ├── REQUEST.cpy          # Request data structure
│   ├── RESPONSE.cpy          # Response buffer structure
│   └── TOOL.cpy             # Tool definitions
├── Makefile                 # Build configuration
├── Dockerfile               # Container build
└── README.md                # This file

sudo apt-get install gnucobol make

brew install gnucobol

make

docker build -t cbl-mcp-server .

./mcp-server

docker run --rm -i cbl-mcp-server

# Test with Docker (default)
node test.js

# Or with npm
npm test

# Test with local binary (requires GnuCOBOL installed)
USE_DOCKER=false node test.js

═══════════════════════════════════════════════════════
         CBL-MCP-SERVER TEST SUITE
═══════════════════════════════════════════════════════

  Test 1: Server startup
    ✓ Server started successfully

  Test 2: Initialize request
    ✓ Initialize response is valid

  Test 3: Tools list request
    ✓ Tools list response is valid

  Test 4-7: Tax calculations
    ✓ All tax calculations correct

  Test 8: Ping request
    ✓ Ping response is valid

  Test 9: Unknown method error handling
    ✓ Error response is valid

═══════════════════════════════════════════════════════
  Total: 9 | Passed: 9 ✓ | Failed: 0 ✗
═══════════════════════════════════════════════════════

{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18"}}

{
  "jsonrpc":"2.0",
  "id":1,
  "result":{
    "protocolVersion":"2025-06-18",
    "capabilities":{"tools":{}},
    "serverInfo":{"name":"cbl-mcp","version":"1.0.0"}
  }
}

{"jsonrpc":"2.0","id":2,"method":"tools/list"}

{
  "jsonrpc":"2.0",
  "id":2,
  "result":{
    "tools":[{
      "name":"calculate_tax",
      "description":"Calculate 7.5 percent sales tax on an amount",
      "inputSchema":{
        "type":"object",
        "properties":{
          "amount":{"type":"number","description":"The pre-tax amount"}
        },
        "required":["amount"]
      }
    }]
  }
}

{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"calculate_tax","arguments":{"amount":100}}}

{
  "jsonrpc":"2.0",
  "id":3,
  "result":{
    "content":[{
      "type":"text",
      "text":"Amount 100.00, tax 7.50, total 107.50"
    }]
  }
}

{"jsonrpc":"2.0","id":6,"method":"ping"}

{"jsonrpc":"2.0","id":6,"result":{}}

echo '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"calculate_tax","arguments":{"amount":500}}}' | ./mcp-server

cat << 'EOF' | ./mcp-server
{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18"}}
{"jsonrpc":"2.0","id":2,"method":"tools/list"}
{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"calculate_tax","arguments":{"amount":100}}}
EOF

echo '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"calculate_tax","arguments":{"amount":1000}}}' | docker run --rm -i cbl-mcp-server

You: Calculate the sales tax for a $500 purchase

Claude: [Calls calculate_tax tool]
For a $500 purchase with 7.5% sales tax:
- Tax: $37.50
- Total: $537.50

You: Which costs more after tax: $99.99 or $100?

Claude: [Calls calculate_tax tool twice]
After 7.5% sales tax:
- $99.99 → $107.48 (tax: $7.49)
- $100.00 → $107.50 (tax: $7.50)

$100 actually costs 2 cents more after tax ($107.50 vs $107.48).

You: I have $200 budget. What's the maximum pre-tax price I can afford?

Claude: [Calculates reverse: 200 / 1.075 ≈ 186.05]
With 7.5% tax, $186.05 pre-tax becomes $200.00 total.
Let me verify:
- Pre-tax: $186.05
- Tax (7.5%): $13.95
- Total: $200.00

You can afford items up to $186.05 before tax.

stdin → READ-REQUEST → PARSE-REQUEST → DISPATCH-REQUEST → BUILD-*-RESPONSE → WRITE-RESPONSE → stdout

make clean && make