karatelabs/karate · error · RuntimeException

missing argument for param()

Error message

missing argument for param()

What it means

Generic arity guard inside HttpRequest's private param() invokable: it fires when the dynamic member-call invokes request.param() with zero arguments at runtime. The input at fault is the missing name argument (the query/path parameter key to look up). Any scripted call to param() without a string name — typically from JS-like request chaining — triggers this sentinel RuntimeException.

Solutions

1. Pass the parameter name: request.param('id')
2. If the name comes from a variable, verify the variable is non-null/non-empty before the call
3. Check generated/configured script strings for an elided argument

Example fix

// before
var v = request.param();
// after
var v = request.param('userId');

// ensure the argument is present and non-empty before the call
if (name == null || name.isEmpty()) throw new IllegalArgumentException("param name required");

function requireArg(name, args) { if (args == null || args.length === 0) throw new Error('missing argument for param()'); return name; }

try { var v = request.param('id'); } catch (RuntimeException e) { /* missing-argument misuse; fix the call site */ }

When it happens

Trigger: Invoking request.param() with zero arguments in a script/expression, e.g. request.param() instead of request.param('name').

Common situations: Copy-paste deleting the argument, dynamic generation of the call where the variable holding the param name was empty/null and dropped, typo leaving the parenthesis empty.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• missing argument for paramValues()
• missing argument for paramInt()
• missing argument for paramJson()
• missing argument for header()
• missing argument for headerValues()

AI-assisted analysis of karatelabs/karate@a22eb90246 (2026-09-12). Data as JSON: /api/errors/8376eaed48b6238a. Report an issue: GitHub.

Appendix: source

Thrown at karate-core/src/main/java/io/karatelabs/http/HttpRequest.java:543

        if (headers != null) {
            headers.forEach((name, values) -> {
                if (values != null && !values.isEmpty()) {
                    builder.header(name, values);
                }
            });
        }
        if (body != null) {
            builder.body(getBodyConverted());
        }
        return builder;
    }

    private JavaInvokable param() {
        return args -> {
            if (args.length > 0) {
                return getParam(args[0] + "");
            } else {
                throw new RuntimeException("missing argument for param()");
            }
        };
    }

    private JavaInvokable paramValues() {
        return args -> {
            if (args.length > 0) {
                return getParamValues(args[0] + "");
            } else {
                throw new RuntimeException("missing argument for paramValues()");
            }
        };
    }

    private JavaInvokable paramInt() {
        return args -> {
            if (args.length > 0) {
                String val = getParam(args[0] + "");

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