diff --git a/README.md b/README.md
index 00537c1..2015816 100644
--- a/README.md
+++ b/README.md
@@ -63,7 +63,7 @@ Ten klient API zapewnia interfejsy Java dla Symfonia WebAPI, umożliwiając pły
 
 ## 📦 Informacje o wersji
 
-- **Aktualna wersja**: `0.1.5`
+- **Aktualna wersja**: `0.1.6`
 - **Wymagana wersja Java**: Java 17+
 
 ## 🔓 Licencja
@@ -84,7 +84,7 @@ Możesz dodać bibliotekę do swojego projektu, dołączając zależność z Mav
 <dependency>
     <groupId>pl.wtx.symfonia</groupId>
     <artifactId>symfonia-erp-webapi-client</artifactId>
-    <version>0.1.5</version>
+    <version>0.1.6</version>
 </dependency>
 ```
 
@@ -102,7 +102,7 @@ Następnie dodaj zbudowany artefakt do swojego projektu:
 <dependency>
     <groupId>pl.wtx.symfonia</groupId>
     <artifactId>symfonia-erp-webapi-client</artifactId>
-    <version>0.1.5</version>
+    <version>0.1.6</version>
 </dependency>
 ```
 
diff --git a/pom.xml b/pom.xml
index 11e7642..5ab2c12 100644
--- a/pom.xml
+++ b/pom.xml
@@ -5,7 +5,7 @@
 
 	<groupId>pl.wtx.symfonia</groupId>
 	<artifactId>symfonia-erp-webapi-client</artifactId>
-	<version>0.1.5</version>
+	<version>0.1.6</version>
 	<packaging>jar</packaging>
 
 	<name>Symfonia ERP WebAPI Client</name>
diff --git a/src/main/java/pl/wtx/symfonia/api/client/ContractorsApi.java b/src/main/java/pl/wtx/symfonia/api/client/ContractorsApi.java
index 5e6432b..47c8044 100644
--- a/src/main/java/pl/wtx/symfonia/api/client/ContractorsApi.java
+++ b/src/main/java/pl/wtx/symfonia/api/client/ContractorsApi.java
@@ -28,9 +28,9 @@
 
 
 import pl.wtx.symfonia.api.client.model.ApiError;
-import pl.wtx.symfonia.api.client.model.Contractor;
 import pl.wtx.symfonia.api.client.model.ContractorCriteriaFilter;
 import pl.wtx.symfonia.api.client.model.ContractorListElement;
+import pl.wtx.symfonia.api.client.model.GetContractors200Response;
 
 import java.lang.reflect.Type;
 import java.util.ArrayList;
@@ -87,7 +87,7 @@ public void setCustomBaseUrl(String customBaseUrl) {
      <table border="1">
        <caption>Response Details</caption>
         <tr><td> Status Code </td><td> Description </td><td> Response Headers </td></tr>
-        <tr><td> 200 </td><td> Zwraca kolekcje obiektow Contractor. </td><td>  -  </td></tr>
+        <tr><td> 200 </td><td> Jeśli parametr &#39;id&#39; jest podany, zwracany jest pojedynczy obiekt Contractor. Jeśli parametr &#39;nip&#39; jest podany, zwracana jest lista obiektów Contractor.  </td><td>  -  </td></tr>
         <tr><td> 400 </td><td> Bad Request </td><td>  -  </td></tr>
         <tr><td> 401 </td><td> Unauthorized </td><td>  -  </td></tr>
         <tr><td> 404 </td><td> Not Found </td><td>  -  </td></tr>
@@ -161,20 +161,20 @@ private okhttp3.Call getContractorsValidateBeforeCall(@javax.annotation.Nullable
      * @param id Identyfikator kontrahenta. (optional)
      * @param code Kod kontrahenta. (optional)
      * @param nip Identyfikator NIP kontrahenta. (optional)
-     * @return List&lt;Contractor&gt;
+     * @return GetContractors200Response
      * @throws ApiException If fail to call the API, e.g. server error or cannot deserialize the response body
      * @http.response.details
      <table border="1">
        <caption>Response Details</caption>
         <tr><td> Status Code </td><td> Description </td><td> Response Headers </td></tr>
-        <tr><td> 200 </td><td> Zwraca kolekcje obiektow Contractor. </td><td>  -  </td></tr>
+        <tr><td> 200 </td><td> Jeśli parametr &#39;id&#39; jest podany, zwracany jest pojedynczy obiekt Contractor. Jeśli parametr &#39;nip&#39; jest podany, zwracana jest lista obiektów Contractor.  </td><td>  -  </td></tr>
         <tr><td> 400 </td><td> Bad Request </td><td>  -  </td></tr>
         <tr><td> 401 </td><td> Unauthorized </td><td>  -  </td></tr>
         <tr><td> 404 </td><td> Not Found </td><td>  -  </td></tr>
      </table>
      */
-    public List<Contractor> getContractors(@javax.annotation.Nullable String id, @javax.annotation.Nullable String code, @javax.annotation.Nullable String nip) throws ApiException {
-        ApiResponse<List<Contractor>> localVarResp = getContractorsWithHttpInfo(id, code, nip);
+    public GetContractors200Response getContractors(@javax.annotation.Nullable String id, @javax.annotation.Nullable String code, @javax.annotation.Nullable String nip) throws ApiException {
+        ApiResponse<GetContractors200Response> localVarResp = getContractorsWithHttpInfo(id, code, nip);
         return localVarResp.getData();
     }
 
@@ -184,21 +184,21 @@ public List<Contractor> getContractors(@javax.annotation.Nullable String id, @ja
      * @param id Identyfikator kontrahenta. (optional)
      * @param code Kod kontrahenta. (optional)
      * @param nip Identyfikator NIP kontrahenta. (optional)
-     * @return ApiResponse&lt;List&lt;Contractor&gt;&gt;
+     * @return ApiResponse&lt;GetContractors200Response&gt;
      * @throws ApiException If fail to call the API, e.g. server error or cannot deserialize the response body
      * @http.response.details
      <table border="1">
        <caption>Response Details</caption>
         <tr><td> Status Code </td><td> Description </td><td> Response Headers </td></tr>
-        <tr><td> 200 </td><td> Zwraca kolekcje obiektow Contractor. </td><td>  -  </td></tr>
+        <tr><td> 200 </td><td> Jeśli parametr &#39;id&#39; jest podany, zwracany jest pojedynczy obiekt Contractor. Jeśli parametr &#39;nip&#39; jest podany, zwracana jest lista obiektów Contractor.  </td><td>  -  </td></tr>
         <tr><td> 400 </td><td> Bad Request </td><td>  -  </td></tr>
         <tr><td> 401 </td><td> Unauthorized </td><td>  -  </td></tr>
         <tr><td> 404 </td><td> Not Found </td><td>  -  </td></tr>
      </table>
      */
-    public ApiResponse<List<Contractor>> getContractorsWithHttpInfo(@javax.annotation.Nullable String id, @javax.annotation.Nullable String code, @javax.annotation.Nullable String nip) throws ApiException {
+    public ApiResponse<GetContractors200Response> getContractorsWithHttpInfo(@javax.annotation.Nullable String id, @javax.annotation.Nullable String code, @javax.annotation.Nullable String nip) throws ApiException {
         okhttp3.Call localVarCall = getContractorsValidateBeforeCall(id, code, nip, null);
-        Type localVarReturnType = new TypeToken<List<Contractor>>(){}.getType();
+        Type localVarReturnType = new TypeToken<GetContractors200Response>(){}.getType();
         return localVarApiClient.execute(localVarCall, localVarReturnType);
     }
 
@@ -215,16 +215,16 @@ public ApiResponse<List<Contractor>> getContractorsWithHttpInfo(@javax.annotatio
      <table border="1">
        <caption>Response Details</caption>
         <tr><td> Status Code </td><td> Description </td><td> Response Headers </td></tr>
-        <tr><td> 200 </td><td> Zwraca kolekcje obiektow Contractor. </td><td>  -  </td></tr>
+        <tr><td> 200 </td><td> Jeśli parametr &#39;id&#39; jest podany, zwracany jest pojedynczy obiekt Contractor. Jeśli parametr &#39;nip&#39; jest podany, zwracana jest lista obiektów Contractor.  </td><td>  -  </td></tr>
         <tr><td> 400 </td><td> Bad Request </td><td>  -  </td></tr>
         <tr><td> 401 </td><td> Unauthorized </td><td>  -  </td></tr>
         <tr><td> 404 </td><td> Not Found </td><td>  -  </td></tr>
      </table>
      */
-    public okhttp3.Call getContractorsAsync(@javax.annotation.Nullable String id, @javax.annotation.Nullable String code, @javax.annotation.Nullable String nip, final ApiCallback<List<Contractor>> _callback) throws ApiException {
+    public okhttp3.Call getContractorsAsync(@javax.annotation.Nullable String id, @javax.annotation.Nullable String code, @javax.annotation.Nullable String nip, final ApiCallback<GetContractors200Response> _callback) throws ApiException {
 
         okhttp3.Call localVarCall = getContractorsValidateBeforeCall(id, code, nip, _callback);
-        Type localVarReturnType = new TypeToken<List<Contractor>>(){}.getType();
+        Type localVarReturnType = new TypeToken<GetContractors200Response>(){}.getType();
         localVarApiClient.executeAsync(localVarCall, localVarReturnType, _callback);
         return localVarCall;
     }
diff --git a/src/main/java/pl/wtx/symfonia/api/client/invoker/JSON.java b/src/main/java/pl/wtx/symfonia/api/client/invoker/JSON.java
index 489f9a9..64e94eb 100644
--- a/src/main/java/pl/wtx/symfonia/api/client/invoker/JSON.java
+++ b/src/main/java/pl/wtx/symfonia/api/client/invoker/JSON.java
@@ -102,6 +102,7 @@ private static Class getClassByDiscriminator(Map classByDiscriminatorValue, Stri
         gsonBuilder.registerTypeAdapterFactory(new pl.wtx.symfonia.api.client.model.ContractorCriteriaFilter.CustomTypeAdapterFactory());
         gsonBuilder.registerTypeAdapterFactory(new pl.wtx.symfonia.api.client.model.ContractorListElement.CustomTypeAdapterFactory());
         gsonBuilder.registerTypeAdapterFactory(new pl.wtx.symfonia.api.client.model.Dimension.CustomTypeAdapterFactory());
+        gsonBuilder.registerTypeAdapterFactory(new pl.wtx.symfonia.api.client.model.GetContractors200Response.CustomTypeAdapterFactory());
         gsonBuilder.registerTypeAdapterFactory(new pl.wtx.symfonia.api.client.model.InventoryState.CustomTypeAdapterFactory());
         gsonBuilder.registerTypeAdapterFactory(new pl.wtx.symfonia.api.client.model.LoadedModuleInfo.CustomTypeAdapterFactory());
         gsonBuilder.registerTypeAdapterFactory(new pl.wtx.symfonia.api.client.model.Order.CustomTypeAdapterFactory());
diff --git a/src/main/java/pl/wtx/symfonia/api/client/model/GetContractors200Response.java b/src/main/java/pl/wtx/symfonia/api/client/model/GetContractors200Response.java
new file mode 100644
index 0000000..f5ff06a
--- /dev/null
+++ b/src/main/java/pl/wtx/symfonia/api/client/model/GetContractors200Response.java
@@ -0,0 +1,300 @@
+/*
+ * Symfonia WebAPI
+ * Symfonia WebAPI - specyfikacja wybranych endpointow API systemu ERP Symfonia. Modele danych sa uproszczone i ograniczone do niektorych parametrow (wersja rozwojowa).
+ *
+ * The version of the OpenAPI document: 1.0.0
+ * 
+ *
+ * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
+ * https://openapi-generator.tech
+ * Do not edit the class manually.
+ */
+
+
+package pl.wtx.symfonia.api.client.model;
+
+import java.util.Objects;
+import com.google.gson.TypeAdapter;
+import com.google.gson.annotations.JsonAdapter;
+import com.google.gson.annotations.SerializedName;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonWriter;
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.List;
+import pl.wtx.symfonia.api.client.model.Contractor;
+import pl.wtx.symfonia.api.client.model.PaymentForm;
+import pl.wtx.symfonia.api.client.model.PaymentRegistry;
+
+
+
+import java.io.IOException;
+import java.lang.reflect.Type;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonParseException;
+import com.google.gson.TypeAdapter;
+import com.google.gson.TypeAdapterFactory;
+import com.google.gson.reflect.TypeToken;
+import com.google.gson.JsonPrimitive;
+import com.google.gson.annotations.JsonAdapter;
+import com.google.gson.annotations.SerializedName;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonWriter;
+import com.google.gson.JsonDeserializationContext;
+import com.google.gson.JsonDeserializer;
+import com.google.gson.JsonSerializationContext;
+import com.google.gson.JsonSerializer;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonArray;
+import com.google.gson.JsonParseException;
+
+import pl.wtx.symfonia.api.client.invoker.JSON;
+
+@javax.annotation.Generated(value = "org.openapitools.codegen.languages.JavaClientCodegen", comments = "Generator version: 7.15.0")
+public class GetContractors200Response extends AbstractOpenApiSchema {
+    private static final Logger log = Logger.getLogger(GetContractors200Response.class.getName());
+
+    public static class CustomTypeAdapterFactory implements TypeAdapterFactory {
+        @SuppressWarnings("unchecked")
+        @Override
+        public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
+            if (!GetContractors200Response.class.isAssignableFrom(type.getRawType())) {
+                return null; // this class only serializes 'GetContractors200Response' and its subtypes
+            }
+            final TypeAdapter<JsonElement> elementAdapter = gson.getAdapter(JsonElement.class);
+            final TypeAdapter<Contractor> adapterContractor = gson.getDelegateAdapter(this, TypeToken.get(Contractor.class));
+
+            final Type typeInstanceListContractor = new TypeToken<List<Contractor>>(){}.getType();
+            final TypeAdapter<List<Contractor>> adapterListContractor = (TypeAdapter<List<Contractor>>) gson.getDelegateAdapter(this, TypeToken.get(typeInstanceListContractor));
+
+            return (TypeAdapter<T>) new TypeAdapter<GetContractors200Response>() {
+                @Override
+                public void write(JsonWriter out, GetContractors200Response value) throws IOException {
+                    if (value == null || value.getActualInstance() == null) {
+                        elementAdapter.write(out, null);
+                        return;
+                    }
+
+                    // check if the actual instance is of the type `Contractor`
+                    if (value.getActualInstance() instanceof Contractor) {
+                        JsonElement element = adapterContractor.toJsonTree((Contractor)value.getActualInstance());
+                        elementAdapter.write(out, element);
+                        return;
+                    }
+                    // check if the actual instance is of the type `List<Contractor>`
+                    if (value.getActualInstance() instanceof List<?>) {
+                        List<?> list = (List<?>) value.getActualInstance();
+                        if (!list.isEmpty() && list.get(0) instanceof Contractor) {
+                            JsonArray array = adapterListContractor.toJsonTree((List<Contractor>)value.getActualInstance()).getAsJsonArray();
+                            elementAdapter.write(out, array);
+                            return;
+                        }
+                    }
+                    throw new IOException("Failed to serialize as the type doesn't match oneOf schemas: Contractor, List<Contractor>");
+                }
+
+                @Override
+                public GetContractors200Response read(JsonReader in) throws IOException {
+                    Object deserialized = null;
+                    JsonElement jsonElement = elementAdapter.read(in);
+
+                    int match = 0;
+                    ArrayList<String> errorMessages = new ArrayList<>();
+                    TypeAdapter actualAdapter = elementAdapter;
+
+                    // deserialize Contractor
+                    try {
+                        // validate the JSON object to see if any exception is thrown
+                        Contractor.validateJsonElement(jsonElement);
+                        actualAdapter = adapterContractor;
+                        match++;
+                        log.log(Level.FINER, "Input data matches schema 'Contractor'");
+                    } catch (Exception e) {
+                        // deserialization failed, continue
+                        errorMessages.add(String.format("Deserialization for Contractor failed with `%s`.", e.getMessage()));
+                        log.log(Level.FINER, "Input data does not match schema 'Contractor'", e);
+                    }
+                    // deserialize List<Contractor>
+                    try {
+                        // validate the JSON object to see if any exception is thrown
+                        if (!jsonElement.isJsonArray()) {
+                            throw new IllegalArgumentException(String.format("Expected json element to be a array type in the JSON string but got `%s`", jsonElement.toString()));
+                        }
+
+                        JsonArray array = jsonElement.getAsJsonArray();
+                        // validate array items
+                        for(JsonElement element : array) {
+                            Contractor.validateJsonElement(element);
+                        }
+                        actualAdapter = adapterListContractor;
+                        match++;
+                        log.log(Level.FINER, "Input data matches schema 'List<Contractor>'");
+                    } catch (Exception e) {
+                        // deserialization failed, continue
+                        errorMessages.add(String.format("Deserialization for List<Contractor> failed with `%s`.", e.getMessage()));
+                        log.log(Level.FINER, "Input data does not match schema 'List<Contractor>'", e);
+                    }
+
+                    if (match == 1) {
+                        GetContractors200Response ret = new GetContractors200Response();
+                        ret.setActualInstance(actualAdapter.fromJsonTree(jsonElement));
+                        return ret;
+                    }
+
+                    throw new IOException(String.format("Failed deserialization for GetContractors200Response: %d classes match result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", match, errorMessages, jsonElement.toString()));
+                }
+            }.nullSafe();
+        }
+    }
+
+    // store a list of schema names defined in oneOf
+    public static final Map<String, Class<?>> schemas = new HashMap<String, Class<?>>();
+
+    public GetContractors200Response() {
+        super("oneOf", Boolean.FALSE);
+    }
+
+    public GetContractors200Response(Object o) {
+        super("oneOf", Boolean.FALSE);
+        setActualInstance(o);
+    }
+
+    static {
+        schemas.put("Contractor", Contractor.class);
+        schemas.put("List<Contractor>", List.class);
+    }
+
+    @Override
+    public Map<String, Class<?>> getSchemas() {
+        return GetContractors200Response.schemas;
+    }
+
+    /**
+     * Set the instance that matches the oneOf child schema, check
+     * the instance parameter is valid against the oneOf child schemas:
+     * Contractor, List<Contractor>
+     *
+     * It could be an instance of the 'oneOf' schemas.
+     */
+    @Override
+    public void setActualInstance(Object instance) {
+        if (instance instanceof Contractor) {
+            super.setActualInstance(instance);
+            return;
+        }
+
+        if (instance instanceof List<?>) {
+            List<?> list = (List<?>) instance;
+            if (!list.isEmpty() && list.get(0) instanceof Contractor) {
+                super.setActualInstance(instance);
+                return;
+            }
+        }
+
+        throw new RuntimeException("Invalid instance type. Must be Contractor, List<Contractor>");
+    }
+
+    /**
+     * Get the actual instance, which can be the following:
+     * Contractor, List<Contractor>
+     *
+     * @return The actual instance (Contractor, List<Contractor>)
+     */
+    @SuppressWarnings("unchecked")
+    @Override
+    public Object getActualInstance() {
+        return super.getActualInstance();
+    }
+
+    /**
+     * Get the actual instance of `Contractor`. If the actual instance is not `Contractor`,
+     * the ClassCastException will be thrown.
+     *
+     * @return The actual instance of `Contractor`
+     * @throws ClassCastException if the instance is not `Contractor`
+     */
+    public Contractor getContractor() throws ClassCastException {
+        return (Contractor)super.getActualInstance();
+    }
+
+    /**
+     * Get the actual instance of `List<Contractor>`. If the actual instance is not `List<Contractor>`,
+     * the ClassCastException will be thrown.
+     *
+     * @return The actual instance of `List<Contractor>`
+     * @throws ClassCastException if the instance is not `List<Contractor>`
+     */
+    public List<Contractor> getListContractor() throws ClassCastException {
+        return (List<Contractor>)super.getActualInstance();
+    }
+
+    /**
+     * Validates the JSON Element and throws an exception if issues found
+     *
+     * @param jsonElement JSON Element
+     * @throws IOException if the JSON Element is invalid with respect to GetContractors200Response
+     */
+    public static void validateJsonElement(JsonElement jsonElement) throws IOException {
+        // validate oneOf schemas one by one
+        int validCount = 0;
+        ArrayList<String> errorMessages = new ArrayList<>();
+        // validate the json string with Contractor
+        try {
+            Contractor.validateJsonElement(jsonElement);
+            validCount++;
+        } catch (Exception e) {
+            errorMessages.add(String.format("Deserialization for Contractor failed with `%s`.", e.getMessage()));
+            // continue to the next one
+        }
+        // validate the json string with List<Contractor>
+        try {
+            if (!jsonElement.isJsonArray()) {
+                throw new IllegalArgumentException(String.format("Expected json element to be a array type in the JSON string but got `%s`", jsonElement.toString()));
+            }
+            JsonArray array = jsonElement.getAsJsonArray();
+            // validate array items
+            for(JsonElement element : array) {
+                Contractor.validateJsonElement(element);
+            }
+            validCount++;
+        } catch (Exception e) {
+            errorMessages.add(String.format("Deserialization for List<Contractor> failed with `%s`.", e.getMessage()));
+            // continue to the next one
+        }
+        if (validCount != 1) {
+            throw new IOException(String.format("The JSON string is invalid for GetContractors200Response with oneOf schemas: Contractor, List<Contractor>. %d class(es) match the result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", validCount, errorMessages, jsonElement.toString()));
+        }
+    }
+
+    /**
+     * Create an instance of GetContractors200Response given an JSON string
+     *
+     * @param jsonString JSON string
+     * @return An instance of GetContractors200Response
+     * @throws IOException if the JSON string is invalid with respect to GetContractors200Response
+     */
+    public static GetContractors200Response fromJson(String jsonString) throws IOException {
+        return JSON.getGson().fromJson(jsonString, GetContractors200Response.class);
+    }
+
+    /**
+     * Convert an instance of GetContractors200Response to an JSON string
+     *
+     * @return JSON string
+     */
+    public String toJson() {
+        return JSON.getGson().toJson(this);
+    }
+}
+