diff --git a/API.md b/API.md
index 6e1907f..202326f 100644
--- a/API.md
+++ b/API.md
@@ -1,3 +1,83 @@
+# Table of contents
+- [Table of contents](#table-of-contents)
+- [1. Description of custom types](#1-description-of-custom-types)
+  - [AccessToken](#accesstoken)
+  - [Building](#building)
+  - [Planet](#planet)
+  - [Research](#research)
+  - [Resource](#resource)
+  - [User](#user)
+- [2. API endpoints](#2-api-endpoints)
+  - [/generateAccessToken](#generateaccesstoken)
+  - [/testAccessToken](#testaccesstoken)
+  - [/planets/getPlanet](#planetsgetplanet)
+  - [/planets/getAllPlanets](#planetsgetallplanets)
+  - [/research/getResearch](#researchgetresearch)
+  - [/research/performResearch](#researchperformresearch)
+  - [/build/createBuilding](#buildcreatebuilding)
+
+# 1. Description of custom types
+
+## AccessToken
+```ts
+_id: ObjectId           // (MongoDB)
+type: "A" | "S" | "X"   // Auth, Spy, Master
+user: ObjectId | null   // master token has this field empty
+entropy: string         // random bytes
+createdAt: Date 
+expiresAt: Date | null  // null for "never expires"
+createdFrom: string
+```
+
+## Building
+```ts
+id: string
+level: number
+```
+
+## Planet
+```ts
+_id: ObjectId,
+owner: User,
+name: string,
+fields: number,
+resources: Array<Resource>,
+buildings: Array<Building>,
+ships: Array<Ship>,
+```
+
+## Research
+```ts
+id: string
+level: number
+```
+
+## Resource
+```ts
+name: string
+amount: number
+lastUpdated: Date
+perHourMiningRate: number
+```
+
+## User
+```ts
+_id: ObjectId
+username: string
+email: string
+password: string           // hashed with argon2
+lastLogin: Date
+research: Array<Research>
+planets: {                 // getting user planets requires second call to DB
+    partial: boolean;      // so by default "partial" is true, and "data" is empty
+    data: Array<Planet>    // unless specified otherwise in code
+}
+createdAt: Date
+updatedAt: Date
+```
+
+# 2. API endpoints
+
 ## /generateAccessToken
 
 **URL: POST** /generateAccessToken
@@ -159,5 +239,4 @@
     "code": 200,
     "message": "OK"
 }
-```
-
+```
\ No newline at end of file