diff --git a/index.d.ts b/index.d.ts
new file mode 100644
index 0000000..751f20a
--- /dev/null
+++ b/index.d.ts
@@ -0,0 +1,24 @@
+declare module 'aqi-bot' {
+  type Result<T extends PollutantType> = {
+    pollutant: T
+    concentration: number
+    aqi: number
+    category: string
+    healthEffectsStatements: string
+    guidanceStatement: string
+  }
+
+  export enum PollutantType {
+    PM10 = "PM10",
+    PM25 = "PM2.5",
+    SO2 = "SO2",
+    NO2 = "NO2",
+    O3 = "O3",
+    CO = "CO",
+  }
+
+  export namespace AQICalculator {
+    export function getAQIResult<T extends PollutantType>(pollutantCode: T, concentration: number): Promise<Result<T>>
+    export function getNowcastAQIResult<T extends PollutantType>(pollutantCode: T, concentrations: number[]): Promise<Result<T>>
+  }
+}