diff --git a/doc/PostmanCollection.schema b/doc/PostmanCollection.schema
new file mode 100644
index 00000000..a6b545a3
--- /dev/null
+++ b/doc/PostmanCollection.schema
@@ -0,0 +1,42 @@
+{
+  "$schema": "http://json-schema.org/draft-06/schema#",
+  "description": "Postman collection",
+  "$ref": "#/definitions/collection",
+  "definitions": {
+    "group": {
+      "type": "object",
+      "properties": {
+        "item": {
+          "type": "array",
+          "items": {
+            "$ref": "#/definitions/collection"
+          }
+        }
+      }
+    },
+    "item": {
+      "type": "object",
+      "properties": {
+        "name": { "type": "string" },
+        "response": {
+          "type": "array",
+          "items": {
+            "$ref": "#/definitions/response"
+          }
+        }
+      }
+    },
+    "response": {
+      "type": "object",
+      "properties": {
+        "body": { "type": "string" }
+      }
+    },
+    "collection": {
+      "oneOf": [
+        { "$ref": "#/definitions/group" },
+        { "$ref": "#/definitions/item" }
+      ]
+    }
+  }
+}
diff --git a/src/PostmanCollection.ts b/src/PostmanCollection.ts
index 5a8a16a7..321c15d6 100644
--- a/src/PostmanCollection.ts
+++ b/src/PostmanCollection.ts
@@ -2,110 +2,39 @@
 
 import { JSONTypeSource } from ".";
 
+function isValidJSON(s: string): boolean {
+    try {
+        JSON.parse(s);
+        return true;
+    } catch (error) {
+        return false;
+    }
+}
+
 export function sourcesFromPostmanCollection(collectionJSON: string): JSONTypeSource[] {
-    const collection = Convert.toPostmanCollection(collectionJSON);
-    return collection.item.map(item => ({ name: item.name, samples: item.response.map(r => r.body) }));
-}
+    const sources: JSONTypeSource[] = [];
 
-interface PostmanCollection {
-    item: Item[];
-}
-
-interface Item {
-    name: string;
-    response: Response[];
-}
-
-interface Response {
-    body: string;
-}
-
-// Converts JSON strings to/from your types
-// and asserts the results of JSON.parse at runtime
-module Convert {
-    export function toPostmanCollection(json: string): PostmanCollection {
-        return cast(JSON.parse(json), O("PostmanCollection"));
-    }
-
-    export function postmanCollectionToJson(value: PostmanCollection): string {
-        return JSON.stringify(value, null, 2);
-    }
-
-    function cast<T>(obj: any, typ: any): T {
-        if (!isValid(typ, obj)) {
-            throw `Invalid value`;
+    function processCollection(c: any): void {
+        if (typeof c !== "object") return;
+        if (Array.isArray(c.item)) {
+            for (const item of c.item) {
+                processCollection(item);
+            }
+        }
+        if (typeof c.name === "string" && Array.isArray(c.response)) {
+            const samples: string[] = [];
+            for (const r of c.response) {
+                if (typeof r === "object" && typeof r.body === "string" && isValidJSON(r.body)) {
+                    samples.push(r.body);
+                }
+            }
+            if (samples.length > 0) {
+                sources.push({ name: c.name, samples });
+            }
         }
-        return obj;
     }
 
-    function isValid(typ: any, val: any): boolean {
-        if (typ === undefined) return true;
-        if (typ === null) return val === null || val === undefined;
-        return typ.isUnion ? isValidUnion(typ.typs, val)
-            : typ.isArray ? isValidArray(typ.typ, val)
-                : typ.isMap ? isValidMap(typ.typ, val)
-                    : typ.isEnum ? isValidEnum(typ.name, val)
-                        : typ.isObject ? isValidObject(typ.cls, val)
-                            : isValidPrimitive(typ, val);
-    }
-
-    function isValidPrimitive(typ: string, val: any) {
-        return typeof typ === typeof val;
-    }
-
-    function isValidUnion(typs: any[], val: any): boolean {
-        // val must validate against one typ in typs
-        return typs.find(typ => isValid(typ, val)) !== undefined;
-    }
-
-    function isValidEnum(enumName: string, val: any): boolean {
-        const cases = typeMap[enumName];
-        return cases.indexOf(val) !== -1;
-    }
-
-    function isValidArray(typ: any, val: any): boolean {
-        // val must be an array with no invalid elements
-        return Array.isArray(val) && val.every(element => {
-            return isValid(typ, element);
-        });
-    }
-
-    function isValidMap(typ: any, val: any): boolean {
-        if (val === null || typeof val !== "object" || Array.isArray(val)) return false;
-        // all values in the map must be typ
-        return Object.keys(val).every(prop => {
-            if (!Object.prototype.hasOwnProperty.call(val, prop)) return true;
-            return isValid(typ, val[prop]);
-        });
-    }
-
-    function isValidObject(className: string, val: any): boolean {
-        if (val === null || typeof val !== "object" || Array.isArray(val)) return false;
-        let typeRep = typeMap[className];
-        return Object.keys(typeRep).every(prop => {
-            if (!Object.prototype.hasOwnProperty.call(typeRep, prop)) return true;
-            return isValid(typeRep[prop], val[prop]);
-        });
-    }
-
-    function A(typ: any) {
-        return { typ, isArray: true };
-    }
-
-    function O(className: string) {
-        return { cls: className, isObject: true };
-    }
-
-    const typeMap: any = {
-        "PostmanCollection": {
-            item: A(O("Item")),
-        },
-        "Item": {
-            name: "",
-            response: A(O("Response")),
-        },
-        "Response": {
-            body: "",
-        },
-    };
+    processCollection(JSON.parse(collectionJSON));
+    console.log("sources are", JSON.stringify(sources));
+    return sources;
 }