diff --git a/src/legacy/core_plugins/vis_type_vega/public/plugin.ts b/src/legacy/core_plugins/vis_type_vega/public/plugin.ts
index 419c5d07fb4b7..039ef49cb2289 100644
--- a/src/legacy/core_plugins/vis_type_vega/public/plugin.ts
+++ b/src/legacy/core_plugins/vis_type_vega/public/plugin.ts
@@ -27,13 +27,11 @@ import { LegacyDependenciesPlugin, LegacyDependenciesPluginSetup } from './shim'
 import { Plugin as DataPublicPlugin } from '../../../../plugins/data/public';
 import { VisualizationsSetup } from '../../visualizations/public';
 
-// @ts-ignore
 import { createVegaFn } from './vega_fn';
-// @ts-ignore
 import { createVegaTypeDefinition } from './vega_type';
 
-/** @private */
-interface VegaVisualizationDependencies extends LegacyDependenciesPluginSetup {
+/** @internal */
+export interface VegaVisualizationDependencies extends LegacyDependenciesPluginSetup {
   uiSettings: UiSettingsClientContract;
 }
 
diff --git a/src/legacy/core_plugins/vis_type_vega/public/vega_fn.js b/src/legacy/core_plugins/vis_type_vega/public/vega_fn.ts
similarity index 66%
rename from src/legacy/core_plugins/vis_type_vega/public/vega_fn.js
rename to src/legacy/core_plugins/vis_type_vega/public/vega_fn.ts
index e92d51668989c..6bbeec38039aa 100644
--- a/src/legacy/core_plugins/vis_type_vega/public/vega_fn.js
+++ b/src/legacy/core_plugins/vis_type_vega/public/vega_fn.ts
@@ -19,16 +19,35 @@
 
 import { get } from 'lodash';
 import { i18n } from '@kbn/i18n';
+
+import { ExpressionFunction, KibanaContext, Render } from '../../interpreter/types';
+import { VegaVisualizationDependencies } from './plugin';
 import { createVegaRequestHandler } from './vega_request_handler';
 
-export const createVegaFn = (dependencies) => ({
-  name: 'vega',
+const name = 'vega';
+type Context = KibanaContext | null;
+
+interface Arguments {
+  spec: string;
+}
+
+export type VisParams = Required<Arguments>;
+
+interface RenderValue {
+  visData: Context;
+  visType: typeof name;
+  visConfig: VisParams;
+}
+
+type Return = Promise<Render<RenderValue>>;
+
+export const createVegaFn = (
+  dependencies: VegaVisualizationDependencies
+): ExpressionFunction<typeof name, Context, Arguments, Return> => ({
+  name,
   type: 'render',
   context: {
-    types: [
-      'kibana_context',
-      'null',
-    ],
+    types: ['kibana_context', 'null'],
   },
   help: i18n.translate('visTypeVega.function.help', {
     defaultMessage: 'Vega visualization',
@@ -37,17 +56,17 @@ export const createVegaFn = (dependencies) => ({
     spec: {
       types: ['string'],
       default: '',
+      help: '',
     },
   },
   async fn(context, args) {
     const vegaRequestHandler = createVegaRequestHandler(dependencies);
 
     const response = await vegaRequestHandler({
-      timeRange: get(context, 'timeRange', null),
-      query: get(context, 'query', null),
-      filters: get(context, 'filters', null),
+      timeRange: get(context, 'timeRange'),
+      query: get(context, 'query'),
+      filters: get(context, 'filters'),
       visParams: { spec: args.spec },
-      forceFetch: true,
     });
 
     return {
@@ -55,7 +74,7 @@ export const createVegaFn = (dependencies) => ({
       as: 'visualization',
       value: {
         visData: response,
-        visType: 'vega',
+        visType: name,
         visConfig: {
           spec: args.spec,
         },
diff --git a/src/legacy/core_plugins/vis_type_vega/public/vega_request_handler.js b/src/legacy/core_plugins/vis_type_vega/public/vega_request_handler.ts
similarity index 69%
rename from src/legacy/core_plugins/vis_type_vega/public/vega_request_handler.js
rename to src/legacy/core_plugins/vis_type_vega/public/vega_request_handler.ts
index 1bffafded4474..a930e369c3e1c 100644
--- a/src/legacy/core_plugins/vis_type_vega/public/vega_request_handler.js
+++ b/src/legacy/core_plugins/vis_type_vega/public/vega_request_handler.ts
@@ -16,18 +16,38 @@
  * specific language governing permissions and limitations
  * under the License.
  */
-import { timefilter } from 'ui/timefilter';
-import { buildEsQuery, getEsQueryConfig } from '@kbn/es-query';
+import { Filter } from '@kbn/es-query';
+import { timefilter, TimeRange } from 'ui/timefilter';
+import { Query } from 'src/legacy/core_plugins/data/public';
 
+// @ts-ignore
+import { buildEsQuery, getEsQueryConfig } from '@kbn/es-query';
+// @ts-ignore
 import { VegaParser } from './data_model/vega_parser';
+// @ts-ignore
 import { SearchCache } from './data_model/search_cache';
+// @ts-ignore
 import { TimeCache } from './data_model/time_cache';
 
-export function createVegaRequestHandler({ uiSettings, es, serviceSettings }) {
+import { VegaVisualizationDependencies } from './plugin';
+import { VisParams } from './vega_fn';
+
+interface VegaRequestHandlerParams {
+  query: Query;
+  filters: Filter;
+  timeRange: TimeRange;
+  visParams: VisParams;
+}
+
+export function createVegaRequestHandler({
+  es,
+  uiSettings,
+  serviceSettings,
+}: VegaVisualizationDependencies) {
   const searchCache = new SearchCache(es, { max: 10, maxAge: 4 * 1000 });
   const timeCache = new TimeCache(timefilter, 3 * 1000);
 
-  return ({ timeRange, filters, query, visParams }) => {
+  return ({ timeRange, filters, query, visParams }: VegaRequestHandlerParams) => {
     timeCache.setTimeRange(timeRange);
 
     const esQueryConfigs = getEsQueryConfig(uiSettings);
diff --git a/src/legacy/core_plugins/vis_type_vega/public/vega_type.js b/src/legacy/core_plugins/vis_type_vega/public/vega_type.ts
similarity index 91%
rename from src/legacy/core_plugins/vis_type_vega/public/vega_type.js
rename to src/legacy/core_plugins/vis_type_vega/public/vega_type.ts
index b4e516cd873f1..6ffcd8867ffea 100644
--- a/src/legacy/core_plugins/vis_type_vega/public/vega_type.js
+++ b/src/legacy/core_plugins/vis_type_vega/public/vega_type.ts
@@ -18,19 +18,23 @@
  */
 
 import { i18n } from '@kbn/i18n';
-import { DefaultEditorSize } from 'ui/vis/editor_size';
 import { Status } from 'ui/vis/update_status';
+// @ts-ignore
+import { DefaultEditorSize } from 'ui/vis/editor_size';
+// @ts-ignore
 import { defaultFeedbackMessage } from 'ui/vis/default_feedback_message';
 
+import vegaEditorTemplate from './vega_editor_template.html';
+import { visFactory } from '../../visualizations/public';
+import { VegaVisualizationDependencies } from './plugin';
+
 import { createVegaRequestHandler } from './vega_request_handler';
+// @ts-ignore
 import { createVegaVisualization } from './vega_visualization';
-
-import vegaEditorTemplate from './vega_editor_template.html';
+// @ts-ignore
 import defaultSpec from '!!raw-loader!./default.spec.hjson';
 
-import { visFactory } from '../../visualizations/public';
-
-export const createVegaTypeDefinition = (dependencies) => {
+export const createVegaTypeDefinition = (dependencies: VegaVisualizationDependencies) => {
   const requestHandler = createVegaRequestHandler(dependencies);
   const visualization = createVegaVisualization(dependencies);
 
diff --git a/src/legacy/ui/public/timefilter/index.d.ts b/src/legacy/ui/public/timefilter/index.d.ts
index db6ead9d17a18..ce1ae86bb93ba 100644
--- a/src/legacy/ui/public/timefilter/index.d.ts
+++ b/src/legacy/ui/public/timefilter/index.d.ts
@@ -18,3 +18,4 @@
  */
 
 export { timefilter, Timefilter } from './timefilter';
+export { timeHistory, TimeRange } from './time_history';