diff --git a/src/core/types.ts b/src/core/types.ts
new file mode 100644
index 0000000..d74cecc
--- /dev/null
+++ b/src/core/types.ts
@@ -0,0 +1,63 @@
+export interface EnvVariable {
+  name: string;
+  value: string;
+  required: boolean;
+  type: EnvType;
+  description?: string;
+  default?: string | number | boolean;
+  choices?: string[];
+}
+
+export type EnvType = 
+  | 'string' 
+  | 'number' 
+  | 'boolean' 
+  | 'enum' 
+  | 'port' 
+  | 'url' 
+  | 'email' 
+  | 'json'
+  | 'int'
+  | 'host';
+
+export interface EnvSchema {
+  variables: Record<string, EnvVariableSchema>;
+}
+
+export interface EnvVariableSchema {
+  type: EnvType;
+  required?: boolean;
+  default?: string | number | boolean;
+  choices?: string[];
+  desc?: string;
+  name?: string;
+}
+
+export interface ParsedEnv {
+  flat: Record<string, string>;
+  nested: Record<string, unknown>;
+}
+
+export interface ValidationResult {
+  valid: boolean;
+  errors: ValidationError[];
+  output: Record<string, unknown>;
+}
+
+export interface ValidationError {
+  field: string;
+  message: string;
+  value?: unknown;
+}
+
+export interface GenerateOptions {
+  envPath?: string;
+  schemaPath?: string;
+  outputPath?: string;
+  interfaceName?: string;
+}
+
+export interface MigrateOptions {
+  envPath?: string;
+  outputPath?: string;
+}