diff --git a/src/backends/claude-code/index.ts b/src/backends/claude-code/index.ts
index e0d0c87a..858bd395 100644
--- a/src/backends/claude-code/index.ts
+++ b/src/backends/claude-code/index.ts
@@ -22,7 +22,10 @@ import { CLAUDE_CODE_MODEL_IDS, DEFAULT_CLAUDE_CODE_MODEL } from './models.js';
 /**
  * Format a single CLI parameter for tool guidance documentation.
  */
-function formatParam(key: string, schema: { type: string; required?: boolean }): string {
+function formatParam(
+	key: string,
+	schema: { type: string; required?: boolean; default?: unknown },
+): string {
 	if (schema.type === 'array') {
 		// Array params use repeated flags: --item "a" --item "b"
 		const singular = key.replace(/s$/, '');
@@ -30,6 +33,13 @@ function formatParam(key: string, schema: { type: string; required?: boolean }):
 			? ` --${singular} <string> (repeatable)`
 			: ` [--${singular} <string> (repeatable)]`;
 	}
+	if (schema.type === 'boolean') {
+		// Boolean flags are presence-based: --flag (true) or --no-flag (false), no value argument
+		if (schema.default === true) {
+			return ` [--no-${key}]`;
+		}
+		return ` [--${key}]`;
+	}
 	return schema.required ? ` --${key} <${schema.type}>` : ` [--${key} <${schema.type}>]`;
 }
 
diff --git a/tests/unit/backends/claude-code.test.ts b/tests/unit/backends/claude-code.test.ts
index 1dc8c169..9637b7c2 100644
--- a/tests/unit/backends/claude-code.test.ts
+++ b/tests/unit/backends/claude-code.test.ts
@@ -96,7 +96,7 @@ describe('buildToolGuidance', () => {
 		expect(guidance).toContain('### ReadWorkItem');
 		expect(guidance).toContain('cascade-tools pm read-work-item');
 		expect(guidance).toContain('--workItemId <string>');
-		expect(guidance).toContain('[--includeComments <boolean>]');
+		expect(guidance).toContain('[--includeComments]');
 		expect(guidance).toContain('### Finish');
 		expect(guidance).toContain('--comment <string>');
 	});
@@ -110,7 +110,24 @@ describe('buildToolGuidance', () => {
 
 	it('marks optional params with brackets', () => {
 		const guidance = buildToolGuidance(sampleTools);
-		expect(guidance).toContain('[--includeComments <boolean>]');
+		expect(guidance).toContain('[--includeComments]');
+		expect(guidance).not.toContain('<boolean>');
+	});
+
+	it('renders boolean flags with default:true as --no-flag', () => {
+		const tools: ToolManifest[] = [
+			{
+				name: 'TestTool',
+				description: 'Test.',
+				cliCommand: 'cascade-tools test',
+				parameters: {
+					'include-comments': { type: 'boolean', default: true },
+				},
+			},
+		];
+		const guidance = buildToolGuidance(tools);
+		expect(guidance).toContain('[--no-include-comments]');
+		expect(guidance).not.toContain('<boolean>');
 	});
 
 	it('renders array params as repeatable flags with singular name', () => {