diff --git a/packages/web-api/src/methods.ts b/packages/web-api/src/methods.ts
index ab45936c0..2c86ccd5b 100644
--- a/packages/web-api/src/methods.ts
+++ b/packages/web-api/src/methods.ts
@@ -273,6 +273,7 @@ import type { AdminBarriersCreateArguments, AdminBarriersDeleteArguments, AdminB
 import type { AdminConversationsArchiveArguments, AdminConversationsBulkArchiveArguments, AdminConversationsBulkDeleteArguments, AdminConversationsBulkMoveArguments, AdminConversationsConvertToPrivateArguments, AdminConversationsConvertToPublicArguments, AdminConversationsCreateArguments, AdminConversationsDeleteArguments, AdminConversationsDisconnectSharedArguments, AdminConversationsEKMListOriginalConnectedChannelInfoArguments, AdminConversationsGetConversationPrefsArguments, AdminConversationsGetCustomRetentionArguments, AdminConversationsGetTeamsArguments, AdminConversationsInviteArguments, AdminConversationsLookupArguments, AdminConversationsRemoveCustomRetentionArguments, AdminConversationsRenameArguments, AdminConversationsRestrictAccessAddGroupArguments, AdminConversationsRestrictAccessListGroupsArguments, AdminConversationsRestrictAccessRemoveGroupArguments, AdminConversationsSearchArguments, AdminConversationsSetConversationPrefsArguments, AdminConversationsSetCustomRetentionArguments, AdminConversationsSetTeamsArguments, AdminConversationsUnarchiveArguments } from './types/request/admin/conversations';
 import type { AdminEmojiAddArguments, AdminEmojiAddAliasArguments, AdminEmojiListArguments, AdminEmojiRemoveArguments, AdminEmojiRenameArguments } from './types/request/admin/emoji';
 import type { AdminFunctionsListArguments, AdminFunctionsPermissionsLookupArguments, AdminFunctionsPermissionsSetArguments } from './types/request/admin/functions';
+import type { FunctionsCompleteErrorArguments, FunctionsCompleteSuccessArguments } from './types/request/functions';
 
 /**
  * Generic method definition
@@ -1311,7 +1312,15 @@ export abstract class Methods extends EventEmitter<WebClientEvent> {
   };
 
   public readonly functions = {
+    /**
+     * @description Signal the failure to execute a Custom Function.
+     * @see {@link https://api.slack.com/methods/functions.completeError `functions.completeError` API reference}.
+     */
     completeError: bindApiCall<FunctionsCompleteErrorArguments, FunctionsCompleteErrorResponse>(this, 'functions.completeError'),
+    /**
+     * @description Signal the successful completion of a Custom Function.
+     * @see {@link https://api.slack.com/methods/functions.completeSuccess `functions.completeSuccess` API reference}.
+     */
     completeSuccess: bindApiCall<FunctionsCompleteSuccessArguments, FunctionsCompleteSuccessResponse>(
       this,
       'functions.completeSuccess',
@@ -1957,17 +1966,4 @@ export interface AdminWorkflowsUnpublishArguments extends TokenOverridable {
   workflow_ids: string[];
 }
 
-/*
- * `functions.*`
- */
-export interface FunctionsCompleteErrorArguments extends TokenOverridable {
-  function_execution_id: string;
-  error: string;
-}
-
-export interface FunctionsCompleteSuccessArguments extends TokenOverridable {
-  function_execution_id: string;
-  outputs: Record<string, unknown>;
-}
-
 export * from '@slack/types';
diff --git a/packages/web-api/src/types/request/files.ts b/packages/web-api/src/types/request/files.ts
index ccaa26049..32c5b9009 100644
--- a/packages/web-api/src/types/request/files.ts
+++ b/packages/web-api/src/types/request/files.ts
@@ -1,5 +1,5 @@
 import type { Stream } from 'node:stream';
-import { CursorPaginationEnabled, OptionalTeamAssignable, TokenOverridable, TraditionalPagingEnabled } from './common';
+import type { CursorPaginationEnabled, OptionalTeamAssignable, TokenOverridable, TraditionalPagingEnabled } from './common';
 import type { FilesGetUploadURLExternalResponse } from '../response';
 
 interface FileArgument {
diff --git a/packages/web-api/src/types/request/functions.ts b/packages/web-api/src/types/request/functions.ts
new file mode 100644
index 000000000..b00aaf1bd
--- /dev/null
+++ b/packages/web-api/src/types/request/functions.ts
@@ -0,0 +1,15 @@
+import type { TokenOverridable } from './common';
+
+interface ExecutionID {
+  function_execution_id: string;
+}
+
+// https://api.slack.com/methods/functions.completeError
+export interface FunctionsCompleteErrorArguments extends ExecutionID, TokenOverridable {
+  error: string;
+}
+
+// https://api.slack.com/methods/functions.completeSuccess
+export interface FunctionsCompleteSuccessArguments extends ExecutionID, TokenOverridable {
+  outputs: Record<string, unknown>;
+}
diff --git a/packages/web-api/test/types/methods/functions.test-d.ts b/packages/web-api/test/types/methods/functions.test-d.ts
new file mode 100644
index 000000000..20e8814bf
--- /dev/null
+++ b/packages/web-api/test/types/methods/functions.test-d.ts
@@ -0,0 +1,36 @@
+import { expectAssignable, expectError } from 'tsd';
+import { WebClient } from '../../../src/WebClient';
+
+const web = new WebClient('TOKEN');
+
+// functions.completeError
+// -- sad path
+expectError(web.functions.completeError()); // lacking argument
+expectError(web.functions.completeError({})); // empty argument
+expectError(web.functions.completeError({
+  function_execution_id: 'Fx1234', // missing error
+}));
+expectError(web.functions.completeError({
+  error: 'boomsies', // missing function_execution_id
+}));
+// -- happy path
+expectAssignable<Parameters<typeof web.functions.completeError>>([{
+  function_execution_id: 'Fx1234',
+  error: 'oh noes',
+}]);
+
+// functions.completeSuccess
+// -- sad path
+expectError(web.functions.completeSuccess()); // lacking argument
+expectError(web.functions.completeSuccess({})); // empty argument
+expectError(web.functions.completeSuccess({
+  function_execution_id: 'Fx1234', // missing output
+}));
+expectError(web.functions.completeSuccess({
+  outputs: {}, // missing function_execution_id
+}));
+// -- happy path
+expectAssignable<Parameters<typeof web.functions.completeSuccess>>([{
+  function_execution_id: 'Fx1234',
+  outputs: {},
+}]);