mcp.zig

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Calculator Server Example ​

This example demonstrates argument validation and deterministic tool behavior.

What This Example Includes ​

  • add tool
  • subtract tool
  • multiply tool
  • divide tool (division-by-zero handling)
  • logging and tasks capabilities

Tool Arguments ​

All tools expect numeric arguments:

  • a
  • b

Build and Run ​

bash
zig build
./zig-out/bin/calculator-server

PowerShell (Windows):

powershell
zig build
.\zig-out\bin\calculator-server.exe

The calculator example runs over stdio by default (CI/GitHub Actions friendly). To test with curl/HTTP, switch the run mode in examples/calculator_server.zig to:

zig
try server.run(io, allocator, .{ .http = .{ .host = "localhost", .port = 8080 } });

HTTP Request Example ​

bash
curl -X POST http://localhost:8080 \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"multiply","arguments":{"a":7,"b":8}}}'

Error Example ​

bash
curl -X POST http://localhost:8080 \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"divide","arguments":{"a":10,"b":0}}}'

The divide tool returns an MCP error result payload for divide-by-zero.

Source ​

See examples/calculator_server.zig for full code.

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