diff --git a/package.json b/package.json
index 9a9fec5..2ea9b92 100644
--- a/package.json
+++ b/package.json
@@ -23,6 +23,7 @@
 		"dist"
 	],
 	"type": "module",
+	"sideEffects": false,
 	"main": "./dist/index.js",
 	"module": "./dist/index.js",
 	"types": "./dist/index.d.ts",
diff --git a/src/index.ts b/src/index.ts
index cd2223b..0a1f69a 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,16 +1,10 @@
-/**
- * safe-formdata: Boundary-focused FormData parser
- *
- * See AGENTS.md for design rules and boundary definition.
- */
+import type { ParseResult } from "#types/ParseResult";
 
 export { parse } from "#parse";
 
 export type { IssueCode } from "#types/IssueCode";
 export type { ParseIssue } from "#types/ParseIssue";
-export type { ParseResult } from "#types/ParseResult";
-
-import type { ParseResult } from "#types/ParseResult";
+export type { ParseResult };
 
 export type SuccessResult = Extract<ParseResult, { data: Record<string, string | File> }>;
 export type FailureResult = Extract<ParseResult, { data: null }>;
diff --git a/src/issues/forbiddenKeys.ts b/src/issues/forbiddenKeys.ts
index c2b1467..a228e54 100644
--- a/src/issues/forbiddenKeys.ts
+++ b/src/issues/forbiddenKeys.ts
@@ -14,8 +14,8 @@
  *
  * @see {@link https://github.com/roottool/safe-formdata/blob/main/AGENTS.md#prototype-safety AGENTS.md > Security rules > Prototype safety}
  */
-export const FORBIDDEN_KEYS = new Set<string>([
+export const FORBIDDEN_KEYS: ReadonlySet<string> = new Set([
 	"__proto__",
 	"prototype",
 	"constructor",
-] as const satisfies readonly string[]);
+]);
diff --git a/tsconfig.examples.json b/tsconfig.examples.json
index 570b9b7..89a7d07 100644
--- a/tsconfig.examples.json
+++ b/tsconfig.examples.json
@@ -3,7 +3,8 @@
 	"compilerOptions": {
 		"noEmit": true,
 		"declaration": false,
-		"declarationMap": false
+		"declarationMap": false,
+		"isolatedDeclarations": false
 	},
 	"include": ["examples/**/*.ts"]
 }
diff --git a/tsconfig.json b/tsconfig.json
index 068f743..2e1c930 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -7,6 +7,7 @@
 		"moduleResolution": "nodenext",
 		"rewriteRelativeImportExtensions": true,
 		"erasableSyntaxOnly": true,
+		"isolatedDeclarations": true,
 		"verbatimModuleSyntax": true,
 
 		// Emit
@@ -15,7 +16,6 @@
 		"declarationMap": true,
 		"sourceMap": true,
 		"outDir": "./dist",
-		"removeComments": true,
 
 		// Type Checking (strict mode)
 		"strict": true,