01-args-and-validation

01-args-and-validation

What you’ll learn

• Reading arguments with mcp_args_get
• Validation failures surfacing as isError=true
• Structured output when jq/gojq is available; minimal mode disables the tool entirely

Prereqs

• Bash 3.2+
• jq or gojq required; without it the server enters minimal mode and this example is unavailable

Run

./examples/run 01-args-and-validation

Transcript

> tools/call example-echo-arg {"value":"hi"}
< {"result":{"content":[{"type":"text","text":"You sent: hi"}]}}
> tools/call example-echo-arg {}
< {"error":{"code":-32602,"message":"Missing 'value' argument","isError":true}}

Success criteria

• tools/list shows example-echo-arg
• Valid call echoes the provided value; missing argument yields a validation error

Troubleshooting

• Ensure scripts are executable (chmod +x examples/run examples/01-args-and-validation/tools/*/tool.sh).
• Install jq/gojq; minimal mode disables tools/resources/prompts.
• Avoid CRLF in requests; send LF-only NDJSON.