diff --git a/src/backends/adapter.ts b/src/backends/adapter.ts
index f376210b..20b2a65a 100644
--- a/src/backends/adapter.ts
+++ b/src/backends/adapter.ts
@@ -82,7 +82,7 @@ function getToolManifests(): ToolManifest[] {
 			parameters: {
 				workItemId: { type: 'string', required: true },
 				name: { type: 'string', required: true },
-				items: { type: 'array', required: true },
+				item: { type: 'array', required: true },
 			},
 		},
 		{
diff --git a/src/backends/claude-code/index.ts b/src/backends/claude-code/index.ts
index c2fc737f..e0d0c87a 100644
--- a/src/backends/claude-code/index.ts
+++ b/src/backends/claude-code/index.ts
@@ -19,6 +19,20 @@ import type {
 import { buildHooks } from './hooks.js';
 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 {
+	if (schema.type === 'array') {
+		// Array params use repeated flags: --item "a" --item "b"
+		const singular = key.replace(/s$/, '');
+		return schema.required
+			? ` --${singular} <string> (repeatable)`
+			: ` [--${singular} <string> (repeatable)]`;
+	}
+	return schema.required ? ` --${key} <${schema.type}>` : ` [--${key} <${schema.type}>]`;
+}
+
 /**
  * Build prompt guidance for CASCADE-specific CLI tools.
  * The Claude Code agent invokes these via its built-in Bash tool.
@@ -41,8 +55,7 @@ export function buildToolGuidance(tools: ToolManifest[]): string {
 		guidance += `\`\`\`bash\n${tool.cliCommand}`;
 
 		for (const [key, schema] of Object.entries(tool.parameters)) {
-			const s = schema as { type: string; required?: boolean };
-			guidance += s.required ? ` --${key} <${s.type}>` : ` [--${key} <${s.type}>]`;
+			guidance += formatParam(key, schema as { type: string; required?: boolean });
 		}
 
 		guidance += '\n```\n\n';
diff --git a/src/cli/pm/add-checklist.ts b/src/cli/pm/add-checklist.ts
index aa271d2e..80ef2470 100644
--- a/src/cli/pm/add-checklist.ts
+++ b/src/cli/pm/add-checklist.ts
@@ -8,8 +8,8 @@ export default class AddChecklist extends CredentialScopedCommand {
 	static override flags = {
 		workItemId: Flags.string({ description: 'The work item ID', required: true }),
 		name: Flags.string({ description: 'Checklist name', required: true }),
-		items: Flags.string({
-			description: 'Checklist items (can be specified multiple times)',
+		item: Flags.string({
+			description: 'Checklist item (repeatable, specify multiple times)',
 			required: true,
 			multiple: true,
 		}),
@@ -20,7 +20,7 @@ export default class AddChecklist extends CredentialScopedCommand {
 		const result = await addChecklist({
 			workItemId: flags.workItemId,
 			checklistName: flags.name,
-			items: flags.items,
+			items: flags.item,
 		});
 		this.log(JSON.stringify({ success: true, data: result }));
 	}
diff --git a/tests/unit/backends/claude-code.test.ts b/tests/unit/backends/claude-code.test.ts
index ceb97a02..1dc8c169 100644
--- a/tests/unit/backends/claude-code.test.ts
+++ b/tests/unit/backends/claude-code.test.ts
@@ -112,6 +112,38 @@ describe('buildToolGuidance', () => {
 		const guidance = buildToolGuidance(sampleTools);
 		expect(guidance).toContain('[--includeComments <boolean>]');
 	});
+
+	it('renders array params as repeatable flags with singular name', () => {
+		const tools: ToolManifest[] = [
+			{
+				name: 'AddChecklist',
+				description: 'Add a checklist.',
+				cliCommand: 'cascade-tools pm add-checklist',
+				parameters: {
+					workItemId: { type: 'string', required: true },
+					item: { type: 'array', required: true },
+				},
+			},
+		];
+		const guidance = buildToolGuidance(tools);
+		expect(guidance).toContain('--item <string> (repeatable)');
+		expect(guidance).not.toContain('<array>');
+	});
+
+	it('renders optional array params with brackets and repeatable hint', () => {
+		const tools: ToolManifest[] = [
+			{
+				name: 'TestTool',
+				description: 'Test.',
+				cliCommand: 'cascade-tools test',
+				parameters: {
+					tags: { type: 'array' },
+				},
+			},
+		];
+		const guidance = buildToolGuidance(tools);
+		expect(guidance).toContain('[--tag <string> (repeatable)]');
+	});
 });
 
 describe('buildTaskPrompt', () => {