googleapis/mcp-toolbox · error

error creating decoder: %w

Error message

error creating decoder: %w

What it means

ParseParameter calls util.NewStrictDecoder on the raw parameter map before dispatching on type. This wrapping error fires when strict-decoder construction fails (e.g. the map cannot be marshaled for decoding); the underlying cause is carried via %w. It is a generic guard at the front of parameter decoding, not a type-specific check.

Source

Thrown at internal/util/parameters/parameters.go:417

	}

	param, err := ParseParameter(ctx, p, typeStr)
	if err != nil {
		return nil, err
	}

	if err := validateParameter(param); err != nil {
		return nil, err
	}

	return param, nil
}

// ParseParameter parses a raw map into a Parameter object based on its "type" field.
func ParseParameter(ctx context.Context, p map[string]any, paramType string) (Parameter, error) {
	dec, err := util.NewStrictDecoder(p)
	if err != nil {
		return nil, fmt.Errorf("error creating decoder: %w", err)
	}
	switch paramType {
	case TypeString:
		a := &StringParameter{}
		if err := dec.DecodeContext(ctx, a); err != nil {
			return nil, fmt.Errorf("unable to parse as %q: %w", paramType, err)
		}
		return a, nil
	case TypeInt:
		a := &IntParameter{}
		if err := dec.DecodeContext(ctx, a); err != nil {
			return nil, fmt.Errorf("unable to parse as %q: %w", paramType, err)
		}
		if a.GetEmbeddedBy() != "" {
			return nil, fmt.Errorf("parameter type %q cannot specify 'embeddedBy'", paramType)
		}
		return a, nil
	case TypeFloat:

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Inspect the wrapped cause to identify the malformed parameter map
2. Ensure the parameter entry is a plain YAML mapping with scalar-compatible values

When it happens

Trigger: Thrown at internal/util/parameters/parameters.go:417 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/a51fdc6148e2cfa7. Report an issue: GitHub.