googleapis/mcp-toolbox · error

logging format invalid: %s

Error message

logging format invalid: %s

What it means

Error "logging format invalid: %s" thrown in googleapis/mcp-toolbox.

Source

Thrown at internal/log/log.go:33

package log

import (
	"context"
	"fmt"
	"io"
	"log/slog"
	"strings"
)

// NewLogger creates a new logger based on the provided format and level.
func NewLogger(format, level string, out, err io.Writer) (Logger, error) {
	switch strings.ToLower(format) {
	case "json":
		return NewStructuredLogger(out, err, level)
	case "standard":
		return NewStdLogger(out, err, level)
	default:
		return nil, fmt.Errorf("logging format invalid: %s", format)
	}
}

// StdLogger is the standard logger
type StdLogger struct {
	outLogger *slog.Logger
	errLogger *slog.Logger
}

// NewStdLogger create a Logger that uses out and err for informational and error messages.
func NewStdLogger(outW, errW io.Writer, logLevel string) (Logger, error) {
	//Set log level
	var programLevel = new(slog.LevelVar)
	slogLevel, err := SeverityToLevel(logLevel)
	if err != nil {
		return nil, err
	}
	programLevel.Set(slogLevel)

View on GitHub (pinned to 8cc6e09de2)

When it happens

Trigger: Thrown at internal/log/log.go:33 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/4051be19ace441a9. Report an issue: GitHub.