diff --git a/src/RobinTTY.NordigenApiClient.Tests/LiveApi/Endpoints/AgreementsEndpointTests.cs b/src/RobinTTY.NordigenApiClient.Tests/LiveApi/Endpoints/AgreementsEndpointTests.cs
index ec8f187..3dee5b3 100644
--- a/src/RobinTTY.NordigenApiClient.Tests/LiveApi/Endpoints/AgreementsEndpointTests.cs
+++ b/src/RobinTTY.NordigenApiClient.Tests/LiveApi/Endpoints/AgreementsEndpointTests.cs
@@ -101,19 +101,6 @@ public async Task GetAgreement()
         AssertionHelpers.AssertNordigenApiResponseIsSuccessful(deleteResponse, HttpStatusCode.OK);
     }
 
-    /// <summary>
-    /// Tests the retrieval of an agreement with an invalid guid.
-    /// </summary>
-    [Test]
-    public async Task GetAgreementWithInvalidGuid()
-    {
-        const string guid = "f84d7b8-dee4-4cd9-bc6d-842ef78f6028";
-        var response = await _apiClient.AgreementsEndpoint.GetAgreement(guid);
-        AssertionHelpers.AssertNordigenApiResponseIsUnsuccessful(response, HttpStatusCode.BadRequest);
-        AssertionHelpers.AssertBasicResponseMatchesExpectations(response.Error, "Invalid EndUserAgreement ID",
-            $"{guid} is not a valid EndUserAgreement UUID. ");
-    }
-
     /// <summary>
     /// Tests the creation and deletion of an end user agreement.
     /// </summary>
@@ -156,24 +143,20 @@ public async Task CreateAcceptAndDeleteAgreement()
     #region RequestsWithErrors
 
     /// <summary>
-    /// Tests the retrieving of an end user agreement with an invalid institution id.
+    /// Tests the retrieval of an agreement with an invalid guid.
     /// </summary>
     [Test]
-    public async Task GetAgreementWithInvalidInstitutionId()
+    public async Task GetAgreementWithInvalidGuid()
     {
-        var agreement = new CreateAgreementRequest(90, 90,
-            ["balances", "details", "transactions"], "invalid_institution");
+        const string guid = "f84d7b8-dee4-4cd9-bc6d-842ef78f6028";
 
-        var response = await _apiClient.AgreementsEndpoint.CreateAgreement(agreement);
+        var response = await _apiClient.AgreementsEndpoint.GetAgreement(guid);
 
-        AssertionHelpers.AssertNordigenApiResponseIsUnsuccessful(response, HttpStatusCode.BadRequest);
         Assert.Multiple(() =>
         {
-            Assert.That(response.Error!.InstitutionIdError, Is.Not.Null);
-            Assert.That(response.Error!.InstitutionIdError!.Summary,
-                Is.EqualTo("Unknown Institution ID invalid_institution"));
-            Assert.That(response.Error!.InstitutionIdError!.Detail,
-                Is.EqualTo("Get Institution IDs from /institutions/?country={$COUNTRY_CODE}"));
+            AssertionHelpers.AssertNordigenApiResponseIsUnsuccessful(response, HttpStatusCode.BadRequest);
+            AssertionHelpers.AssertBasicResponseMatchesExpectations(response.Error, "Invalid EndUserAgreement ID",
+                $"{guid} is not a valid EndUserAgreement UUID. ");
         });
     }
 
@@ -232,15 +215,14 @@ public async Task CreateAgreementWithInvalidParamsAtPolishInstitution()
             ["balances", "transactions"], "PKO_BPKOPLPW");
 
         var response = await _apiClient.AgreementsEndpoint.CreateAgreement(agreement);
-        var result = response.Error!;
 
         Assert.Multiple(() =>
         {
             AssertionHelpers.AssertNordigenApiResponseIsUnsuccessful(response, HttpStatusCode.BadRequest);
-            Assert.That(new[] {result.InstitutionIdError, result.AgreementError}, Has.All.Null);
-            Assert.That(result.Detail,
+            Assert.That(new[] {response.Error!.InstitutionIdError, response.Error!.AgreementError}, Has.All.Null);
+            Assert.That(response.Error!.Detail,
                 Is.EqualTo("For this institution the following scopes are required together: ['details', 'balances']"));
-            Assert.That(result.Summary, Is.EqualTo("Institution access scope dependencies error"));
+            Assert.That(response.Error!.Summary, Is.EqualTo("Institution access scope dependencies error"));
         });
     }
 
diff --git a/src/RobinTTY.NordigenApiClient.Tests/Mocks/Endpoints/AgreementsEndpointTests.cs b/src/RobinTTY.NordigenApiClient.Tests/Mocks/Endpoints/AgreementsEndpointTests.cs
index f58a0e6..84b562b 100644
--- a/src/RobinTTY.NordigenApiClient.Tests/Mocks/Endpoints/AgreementsEndpointTests.cs
+++ b/src/RobinTTY.NordigenApiClient.Tests/Mocks/Endpoints/AgreementsEndpointTests.cs
@@ -6,13 +6,16 @@ namespace RobinTTY.NordigenApiClient.Tests.Mocks.Endpoints;
 
 public class AgreementsEndpointTests
 {
+    #region RequestsWithSuccessfulResponse
+
     /// <summary>
     /// Tests the retrieval of end user agreements.
     /// </summary>
     [Test]
     public async Task GetAgreements()
     {
-        var apiClient = TestHelpers.GetMockClient(TestHelpers.MockData.AgreementsEndpointMockData.GetAgreements, HttpStatusCode.OK);
+        var apiClient = TestHelpers.GetMockClient(TestHelpers.MockData.AgreementsEndpointMockData.GetAgreements,
+            HttpStatusCode.OK);
 
         var agreements = await apiClient.AgreementsEndpoint.GetAgreements(100, 0);
         AssertionHelpers.AssertNordigenApiResponseIsSuccessful(agreements, HttpStatusCode.OK);
@@ -50,7 +53,8 @@ public async Task GetAgreements()
     [Test]
     public async Task GetAgreement()
     {
-        var apiClient = TestHelpers.GetMockClient(TestHelpers.MockData.AgreementsEndpointMockData.GetAgreement, HttpStatusCode.OK);
+        var apiClient = TestHelpers.GetMockClient(TestHelpers.MockData.AgreementsEndpointMockData.GetAgreement,
+            HttpStatusCode.OK);
 
         var agreement = await apiClient.AgreementsEndpoint.GetAgreement(A.Dummy<Guid>());
         AssertionHelpers.AssertNordigenApiResponseIsSuccessful(agreement, HttpStatusCode.OK);
@@ -76,7 +80,8 @@ public async Task GetAgreement()
     [Test]
     public async Task CreateAgreement()
     {
-        var apiClient = TestHelpers.GetMockClient(TestHelpers.MockData.AgreementsEndpointMockData.CreateAgreement, HttpStatusCode.Created);
+        var apiClient = TestHelpers.GetMockClient(TestHelpers.MockData.AgreementsEndpointMockData.CreateAgreement,
+            HttpStatusCode.Created);
 
         var agreementRequest = new CreateAgreementRequest(145, 145,
             ["balances", "details", "transactions"], "SANDBOXFINANCE_SFIN0000");
@@ -101,14 +106,118 @@ public async Task CreateAgreement()
     [Test]
     public async Task DeleteAgreement()
     {
-        var apiClient = TestHelpers.GetMockClient(TestHelpers.MockData.AgreementsEndpointMockData.DeleteAgreement, HttpStatusCode.OK);
+        var apiClient = TestHelpers.GetMockClient(TestHelpers.MockData.AgreementsEndpointMockData.DeleteAgreement,
+            HttpStatusCode.OK);
 
         var result = await apiClient.AgreementsEndpoint.DeleteAgreement(A.Dummy<Guid>());
         AssertionHelpers.AssertNordigenApiResponseIsSuccessful(result, HttpStatusCode.OK);
         Assert.Multiple(() =>
         {
             Assert.That(result.Result?.Summary, Is.EqualTo("End User Agreement deleted"));
-            Assert.That(result.Result?.Detail, Is.EqualTo("End User Agreement bb37bc52-5b1d-44f9-b1cd-ec9594f25387 deleted"));
+            Assert.That(result.Result?.Detail,
+                Is.EqualTo("End User Agreement bb37bc52-5b1d-44f9-b1cd-ec9594f25387 deleted"));
+        });
+    }
+
+    #endregion
+
+    #region RequestsWithErrors
+
+    /// <summary>
+    /// Tests the retrieval of an agreement with an invalid guid.
+    /// </summary>
+    [Test]
+    public async Task GetAgreementWithInvalidGuid()
+    {
+        const string guid = "f84d7b8-dee4-4cd9-bc6d-842ef78f6028";
+        var apiClient = TestHelpers.GetMockClient(
+            TestHelpers.MockData.AgreementsEndpointMockData.GetAgreementWithInvalidGuid,
+            HttpStatusCode.BadRequest);
+
+        var response = await apiClient.AgreementsEndpoint.GetAgreement(guid);
+
+        Assert.Multiple(() =>
+        {
+            AssertionHelpers.AssertNordigenApiResponseIsUnsuccessful(response, HttpStatusCode.BadRequest);
+            AssertionHelpers.AssertBasicResponseMatchesExpectations(response.Error, "Invalid EndUserAgreement ID",
+                $"{guid} is not a valid EndUserAgreement UUID. ");
+        });
+    }
+
+    /// <summary>
+    /// Tests the creation of an end user agreement with an invalid institution id.
+    /// </summary>
+    [Test]
+    public async Task CreateAgreementWithInvalidInstitutionId()
+    {
+        var apiClient = TestHelpers.GetMockClient(
+            TestHelpers.MockData.AgreementsEndpointMockData.CreateAgreementWithInvalidInstitutionId,
+            HttpStatusCode.BadRequest);
+        var agreement = new CreateAgreementRequest(90, 90,
+            ["balances", "details", "transactions"], "invalid_institution");
+
+        var response = await apiClient.AgreementsEndpoint.CreateAgreement(agreement);
+
+        AssertionHelpers.AssertNordigenApiResponseIsUnsuccessful(response, HttpStatusCode.BadRequest);
+        Assert.Multiple(() =>
+        {
+            Assert.That(response.Error!.InstitutionIdError, Is.Not.Null);
+            Assert.That(response.Error!.InstitutionIdError!.Summary,
+                Is.EqualTo("Unknown Institution ID invalid_institution"));
+            Assert.That(response.Error!.InstitutionIdError!.Detail,
+                Is.EqualTo("Get Institution IDs from /institutions/?country={$COUNTRY_CODE}"));
         });
     }
+
+    /// <summary>
+    /// Tests the creation of an end user agreement with invalid parameters.
+    /// </summary>
+    [Test]
+    public async Task CreateAgreementWithInvalidParams()
+    {
+        var apiClient = TestHelpers.GetMockClient(
+            TestHelpers.MockData.AgreementsEndpointMockData.CreateAgreementWithInvalidParams,
+            HttpStatusCode.BadRequest);
+        var agreement = new CreateAgreementRequest(200, 200,
+            ["balances", "details", "transactions", "invalid", "invalid2"], "SANDBOXFINANCE_SFIN0000");
+
+        var response = await apiClient.AgreementsEndpoint.CreateAgreement(agreement);
+        var result = response.Error!;
+
+        Assert.Multiple(() =>
+        {
+            AssertionHelpers.AssertNordigenApiResponseIsUnsuccessful(response, HttpStatusCode.BadRequest);
+            Assert.That(new[] {result.InstitutionIdError, result.AgreementError}, Has.All.Null);
+            Assert.That(result.AccessScopeError!.Detail,
+                Is.EqualTo("Choose one or several from ['balances', 'details', 'transactions']"));
+            Assert.That(result.AccessValidForDaysError!.Detail,
+                Is.EqualTo("access_valid_for_days must be > 0 and <= 180"));
+            Assert.That(result.MaxHistoricalDaysError!.Detail,
+                Is.EqualTo(
+                    "max_historical_days must be > 0 and <= SANDBOXFINANCE_SFIN0000 transaction_total_days (90)"));
+        });
+    }
+
+    [Test]
+    public async Task CreateAgreementWithInvalidParamsAtPolishInstitution()
+    {
+        var apiClient = TestHelpers.GetMockClient(
+            TestHelpers.MockData.AgreementsEndpointMockData.CreateAgreementWithInvalidParamsAtPolishInstitution,
+            HttpStatusCode.BadRequest);
+        var agreement = new CreateAgreementRequest(90, 90,
+            ["balances", "transactions"], "PKO_BPKOPLPW");
+
+        var response = await apiClient.AgreementsEndpoint.CreateAgreement(agreement);
+
+        Assert.Multiple(() =>
+        {
+            AssertionHelpers.AssertNordigenApiResponseIsUnsuccessful(response, HttpStatusCode.BadRequest);
+            Assert.That(new[] {response.Error!.InstitutionIdError, response.Error!.AgreementError}, Has.All.Null);
+            Assert.That(response.Error!.Detail,
+                Is.EqualTo("For this institution the following scopes are required together: ['details', 'balances']"));
+            Assert.That(response.Error!.Summary, Is.EqualTo("Institution access scope dependencies error"));
+        });
+    }
+
+    #endregion
 }
diff --git a/src/RobinTTY.NordigenApiClient.Tests/Mocks/Responses/MockResponsesModel.cs b/src/RobinTTY.NordigenApiClient.Tests/Mocks/Responses/MockResponsesModel.cs
index f1f5384..8675aa6 100644
--- a/src/RobinTTY.NordigenApiClient.Tests/Mocks/Responses/MockResponsesModel.cs
+++ b/src/RobinTTY.NordigenApiClient.Tests/Mocks/Responses/MockResponsesModel.cs
@@ -46,12 +46,26 @@ internal class AgreementsEndpointMockData(
     ResponsePage<Agreement> getAgreements,
     Agreement createAgreement,
     Agreement getAgreement,
-    BasicResponse deleteAgreement)
+    BasicResponse deleteAgreement,
+    BasicResponse getAgreementWithInvalidGuid,
+    CreateAgreementError createAgreementWithInvalidInstitutionId,
+    CreateAgreementError createAgreementWithInvalidParams,
+    CreateAgreementError createAgreementWithInvalidParamsAtPolishInstitution)
 {
     public ResponsePage<Agreement> GetAgreements { get; set; } = getAgreements;
     public Agreement CreateAgreement { get; set; } = createAgreement;
     public Agreement GetAgreement { get; set; } = getAgreement;
     public BasicResponse DeleteAgreement { get; set; } = deleteAgreement;
+
+    public BasicResponse GetAgreementWithInvalidGuid { get; set; } = getAgreementWithInvalidGuid;
+
+    public CreateAgreementError CreateAgreementWithInvalidInstitutionId { get; set; } =
+        createAgreementWithInvalidInstitutionId;
+
+    public CreateAgreementError CreateAgreementWithInvalidParams { get; set; } = createAgreementWithInvalidParams;
+
+    public CreateAgreementError CreateAgreementWithInvalidParamsAtPolishInstitution { get; set; } =
+        createAgreementWithInvalidParamsAtPolishInstitution;
 }
 
 internal class InstitutionsEndpointMockData(List<Institution> getInstitutions, Institution getInstitution)
diff --git a/src/RobinTTY.NordigenApiClient.Tests/Mocks/Responses/responses.json b/src/RobinTTY.NordigenApiClient.Tests/Mocks/Responses/responses.json
index 1a00ef2..7dd302e 100644
--- a/src/RobinTTY.NordigenApiClient.Tests/Mocks/Responses/responses.json
+++ b/src/RobinTTY.NordigenApiClient.Tests/Mocks/Responses/responses.json
@@ -199,6 +199,42 @@
     "DeleteAgreement": {
       "summary": "End User Agreement deleted",
       "detail": "End User Agreement bb37bc52-5b1d-44f9-b1cd-ec9594f25387 deleted"
+    },
+    "GetAgreementWithInvalidGuid": {
+      "summary": "Invalid EndUserAgreement ID",
+      "detail": "f84d7b8-dee4-4cd9-bc6d-842ef78f6028 is not a valid EndUserAgreement UUID. ",
+      "status_code": 400
+    },
+    "CreateAgreementWithInvalidInstitutionId": {
+      "institution_id": {
+        "summary": "Unknown Institution ID invalid_institution",
+        "detail": "Get Institution IDs from /institutions/?country\u003d{$COUNTRY_CODE}"
+      },
+      "status_code": 400
+    },
+    "CreateAgreementWithInvalidParams": {
+      "max_historical_days": {
+        "summary": "Incorrect max_historical_days",
+        "detail": "max_historical_days must be \u003e 0 and \u003c\u003d SANDBOXFINANCE_SFIN0000 transaction_total_days (90)"
+      },
+      "access_valid_for_days": {
+        "summary": "Incorrect access_valid_for_days",
+        "detail": "access_valid_for_days must be \u003e 0 and \u003c\u003d 180"
+      },
+      "access_scope": {
+        "summary": "Unknown value \u0027[\u0027invalid2\u0027, \u0027invalid\u0027]\u0027 in access_scope",
+        "detail": "Choose one or several from [\u0027balances\u0027, \u0027details\u0027, \u0027transactions\u0027]"
+      },
+      "status_code": 400
+    },
+    "CreateAgreementWithInvalidParamsAtPolishInstitution": {
+      "summary": [
+        "Institution access scope dependencies error"
+      ],
+      "detail": [
+        "For this institution the following scopes are required together: [\u0027details\u0027, \u0027balances\u0027]"
+      ],
+      "status_code": 400
     }
   },
   "InstitutionsEndpointMockData": {