fix: address review comments - add JSDoc, null test, and clarify default behavior

Author: roomote

src/core/prompts/tools/__tests__/fetch-instructions.spec.ts

@@ -40,4 +40,14 @@ describe("getFetchInstructionsDescription", () => {
 		expect(description).toContain("<fetch_instructions>")
 		expect(description).toContain("</fetch_instructions>")
 	})
+
+	it("should handle null value consistently (treat as default/undefined)", () => {
+		const description = getFetchInstructionsDescription(null as any)
+
+		// Should behave the same as undefined (default to true)
+		expect(description).toContain("create_mcp_server")
+		expect(description).toContain("create_mode")
+		expect(description).toContain("Example: Requesting instructions to create an MCP Server")
+		expect(description).toContain("<task>create_mcp_server</task>")
+	})
 })

src/core/prompts/tools/fetch-instructions.ts

@@ -1,3 +1,8 @@
+/**
+ * Generates the fetch_instructions tool description.
+ * @param enableMcpServerCreation - Whether to include MCP server creation task.
+ *                                  Defaults to true when undefined.
+ */
 export function getFetchInstructionsDescription(enableMcpServerCreation?: boolean): string {
 	const tasks =
 		enableMcpServerCreation !== false