diff --git a/index.d.ts b/index.d.ts
new file mode 100644
index 0000000..89fa7ac
--- /dev/null
+++ b/index.d.ts
@@ -0,0 +1,100 @@
+interface EggMySQLClientOption {
+  /// host e.g. 'mysql.com'
+  host: string;
+  /// port e.g. '3306'
+  port: string;
+  /// username e.g. 'test_user'
+  user: string;
+  // password e.g. 'test_password'
+  password: string;
+  // database e.g. 'test'
+  database: string;
+}
+
+type Singleton<T> = {};
+
+interface EggMySQLClientsOption {
+  [clientName: string]: EggMySQLClientOption;
+}
+
+interface EggMySqlConfig {
+  default?: object;
+  app?: boolean;
+  agent?: boolean;
+  client?: EggMySQLClientOption;
+  clients?: EggMySQLClientsOption;
+}
+
+type EggMySQLInsertResult = object[];
+type EggMySQLSelectResult = object[];
+interface EggMySQLCondition {
+  where?: object;
+  orders?: [string, "desc" | "asc" | "DESC" | "ASC"][];
+  limit?: number;
+  offset?: number;
+  [otherCondition: string]: any;
+}
+interface EggMySQLUpdateResult {
+  affectedRows: number;
+  fieldCount: number;
+  insertId: number;
+  serverStatus: number;
+  warningCount: number;
+  message: string;
+  protocol41: boolean;
+  changedRows: number;
+}
+
+interface EggMySQLLiterals {
+  now: number;
+  Literal: Function;
+}
+
+interface EggMySQL {
+  literals: EggMySQLLiterals;
+  /// Returns mysql client instance.
+  get: (dbName: string) => EggMySQL;
+  /// execute sql e.g.
+  /// query('update posts set hits = (hits + ?) where id = ?', [1, postId])
+  query: (
+    sql: string,
+    values?: any[]
+  ) => Promise<
+    EggMySQLSelectResult | EggMySQLUpdateResult | EggMySQLInsertResult
+  >;
+  /// create object into table
+  create: (table: string, values: object) => Promise<EggMySQLUpdateResult>;
+  /// update object of table
+  update: (table: string, values: object) => Promise<EggMySQLUpdateResult>;
+  /// delete objects from table
+  delete: (table: string, values: object) => Promise<EggMySQLUpdateResult>;
+  /// insert object into table
+  insert: (table: string, values: object) => Promise<EggMySQLInsertResult>;
+  /// select objects from table
+  select: (
+    table: string,
+    condition?: EggMySQLCondition
+  ) => Promise<EggMySQLSelectResult>;
+  /// begin a transaction
+  beginTransaction: () => Promise<EggMySQLTransation>;
+  /// begin a scoped transaction
+  beginTransactionScope: (
+    codeBlock: (conn: EggMySQLTransation) => Promise<object>,
+    ctx: object
+  ) => Promise<EggMySQLTransation>;
+}
+
+interface EggMySQLTransation extends Omit<EggMySQL, "beginTransaction"> {
+  commit: () => Promise<void>;
+  rollback: () => Promise<void>;
+}
+
+declare module "egg" {
+  interface Application {
+    mysql: EggMySQL & Singleton<EggMySQL>;
+  }
+
+  interface EggAppConfig {
+    mysql: EggMySqlConfig;
+  }
+}