googleapis/mcp-toolbox · error

error writing script %s: %w

Error message

error writing script %s: %w

What it means

This error wraps a failure from os.WriteFile when persisting a generated per-tool wrapper script (<toolName>.js) into the skill's scripts directory. The content was generated successfully, but writing it to disk failed — typically a filesystem-level problem such as permissions, a missing parent directory, or a path conflict.

Source

Thrown at cmd/internal/skills/command.go:221

		// Iterate over keys to ensure deterministic order
		var toolNames []string
		for name := range allTools {
			toolNames = append(toolNames, name)
		}
		sort.Strings(toolNames)

		for _, toolName := range toolNames {
			// Generate wrapper script in scripts directory
			scriptContent, err := generateScriptContent(toolName, configArgsStr, cmd.licenseHeader, cmd.invocationMode, cmd.toolboxVersion, parser.OptionalEnvVars)
			if err != nil {
				errMsg := fmt.Errorf("error generating script content for %s: %w", toolName, err)
				opts.Logger.ErrorContext(ctx, errMsg.Error())
				return errMsg
			}

			scriptFilename := filepath.Join(scriptsPath, fmt.Sprintf("%s.js", toolName))
			if err := os.WriteFile(scriptFilename, []byte(scriptContent), 0755); err != nil {
				errMsg := fmt.Errorf("error writing script %s: %w", scriptFilename, err)
				opts.Logger.ErrorContext(ctx, errMsg.Error())
				return errMsg
			}
		}

		// Generate SKILL.md
		skillContent, err := generateSkillMarkdown(skillName, content.description, cmd.additionalNotes, allTools, parser.EnvVars)
		if err != nil {
			errMsg := fmt.Errorf("error generating SKILL.md content: %w", err)
			opts.Logger.ErrorContext(ctx, errMsg.Error())
			return errMsg
		}
		skillMdPath := filepath.Join(skillPath, "SKILL.md")
		if err := os.WriteFile(skillMdPath, []byte(skillContent), 0644); err != nil {
			errMsg := fmt.Errorf("error writing SKILL.md: %w", err)
			opts.Logger.ErrorContext(ctx, errMsg.Error())
			return errMsg
		}

View on GitHub (pinned to 8cc6e09de2)

Solutions

1. Check permissions on the output directory and its scripts/ subdirectory (ls -ld) and chmod/chown as needed
2. Verify the scripts path exists as a directory and is not a regular file (rm or move the conflicting entry)
3. Re-run with a different --output location you have write access to
4. Free disk space or remount the volume read-write if the filesystem is full or read-only

Example fix

// before
mkdir -p ~/.claude/skills/my-skill/scripts && toolbox skills --output ~/.claude/skills/my-skill ...
# scripts/ owned by root -> write fails
// after
sudo chown -R $USER ~/.claude/skills/my-skill && toolbox skills --output ~/.claude/skills/my-skill ...

# Verify the target scripts dir is a writable directory before running
if [ ! -d "$OUT/skills/my-skill/scripts" ] || [ ! -w "$OUT/skills/my-skill/scripts" ]; then
  mkdir -p "$OUT/skills/my-skill/scripts" || exit 1
fi

try {
  execSync("toolbox skills --name my-skill", { stdio: "inherit" });
} catch (e) {
  if (String(e.stderr).includes("error writing script")) {
    console.error("Filesystem write failed; check permissions on the output directory:", e.stderr);
  } else { throw e; }
}

When it happens

Trigger: Running `toolbox skills` when os.WriteFile(scriptFilename, ...) fails — the target scripts directory does not exist or is not writable, the path is not a directory, or the filesystem is full/read-only.

Common situations: Writing a skill into a directory owned by another user or without write permission; the scripts/ path was pre-created as a file; generating into a read-only mounted volume or a path with restrictive umask; disk quota exceeded.

Understand the failure class

Background: "Permission denied" / "Failed to write" file errors: why a library can't write its files to disk (EACCES, EPERM, ENOSPC) and how to fix them — this error's family across 43 libraries.

Related errors

• error writing SKILL.md: %w
• failed to rename file: %w
• error finding YAML files in %q: %w
• error finding YML files in %q: %w
• failed to initialize resources: %w

AI-assisted analysis of googleapis/mcp-toolbox@8cc6e09de2 (2026-09-05). Data as JSON: /api/errors/478181cbfe0b3158. Report an issue: GitHub.