wavetermdev/waveterm · error

missing contents parameter

Error message

missing contents parameter

What it means

Input unmarshaled fine but the required Contents field is the empty string. The write-app-file tool refuses to write an empty file body, treating it as a missing parameter. Because Contents is a string, omitted and "" are indistinguishable here — both trigger this error.

Source

Thrown at pkg/aiusechat/tools_builder.go:71

		"build_success": result.Success,
		"build_error":   result.ErrorMessage,
		"build_output":  result.BuildOutput,
	}
}

func parseBuilderWriteAppFileInput(input any) (*builderWriteAppFileParams, error) {
	result := &builderWriteAppFileParams{}

	if input == nil {
		return nil, fmt.Errorf("input is required")
	}

	if err := utilfn.ReUnmarshal(result, input); err != nil {
		return nil, fmt.Errorf("invalid input format: %w", err)
	}

	if result.Contents == "" {
		return nil, fmt.Errorf("missing contents parameter")
	}

	return result, nil
}

func GetBuilderWriteAppFileToolDefinition(appId string, builderId string) uctypes.ToolDefinition {
	return uctypes.ToolDefinition{
		Name:        "builder_write_app_file",
		DisplayName: "Write App File",
		Description: fmt.Sprintf("Write the app.go file for app %s", appId),
		ToolLogName: "builder:write_app",
		Strict:      false,
		InputSchema: map[string]any{
			"type": "object",
			"properties": map[string]any{
				"contents": map[string]any{
					"type":        "string",
					"description": "The contents to write to app.go",

View on GitHub (pinned to a4447c1563)

Solutions

1. Provide non-empty contents: {"contents": "<file text>"}
2. If the intent is an empty/blank file, pass at least a placeholder (e.g. "\n") or use a delete operation instead
3. Strengthen the tool description to state contents must be non-empty

Example fix

// before
{"file": "app.tsx", "contents": ""}
// after
{"file": "app.tsx", "contents": "export default function App() { return null }"}

if m, ok := input.(map[string]any); ok { if c, _ := m["contents"].(string); c == "" { return errors.New("contents must be a non-empty string") } }

func hasContents(input any) bool { m, ok := input.(map[string]any); if !ok { return false }; s, ok := m["contents"].(string); return ok && s != "" }

params, err := parseBuilderWriteAppFileInput(input); if err != nil && strings.Contains(err.Error(), "missing contents") { return fmt.Errorf("refusing to write empty file: %w", err) }

When it happens

Trigger: Tool called with {} or {"contents": ""} — the contents key absent or explicitly empty after unmarshal.

Common situations: Model generating an empty file body (e.g. it intended to only create the file); prompt asking to 'clear' a file where a delete/edit op was appropriate; truncation cutting off long contents.

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 edits parameter
• missing values parameter
• input is required
• invalid input format: %w
• invalid input format

AI-assisted analysis of wavetermdev/waveterm@a4447c1563 (2026-09-01). Data as JSON: /api/errors/8bdfab29f23571e6. Report an issue: GitHub.