diff --git a/src/legacy/core_plugins/interpreter/public/functions/__snapshots__/kibana.test.js.snap b/src/legacy/core_plugins/interpreter/public/functions/__snapshots__/kibana.test.ts.snap
similarity index 100%
rename from src/legacy/core_plugins/interpreter/public/functions/__snapshots__/kibana.test.js.snap
rename to src/legacy/core_plugins/interpreter/public/functions/__snapshots__/kibana.test.ts.snap
diff --git a/src/legacy/core_plugins/interpreter/public/functions/__tests__/font.js b/src/legacy/core_plugins/interpreter/public/functions/__tests__/font.ts
similarity index 96%
rename from src/legacy/core_plugins/interpreter/public/functions/__tests__/font.js
rename to src/legacy/core_plugins/interpreter/public/functions/__tests__/font.ts
index 4a7ebc1522f2ab..8bf8052fee3b7b 100644
--- a/src/legacy/core_plugins/interpreter/public/functions/__tests__/font.js
+++ b/src/legacy/core_plugins/interpreter/public/functions/__tests__/font.ts
@@ -23,13 +23,13 @@ import { font } from '../font';
 import { functionWrapper } from '../../../test_helpers';
 
 describe('font', () => {
-  const fn = functionWrapper(font);
+  const fn: any = functionWrapper(font);
 
   describe('default output', () => {
     const result = fn(null);
 
     it('returns a style', () => {
-      expect(result)
+      (expect as any)(result)
         .to.have.property('type', 'style')
         .and.to.have.property('spec')
         .and.to.have.property('css');
@@ -40,8 +40,8 @@ describe('font', () => {
     describe('size', () => {
       it('sets font size', () => {
         const result = fn(null, { size: 20 });
-        expect(result.spec).to.have.property('fontSize', '20px');
-        expect(result.css).to.contain('font-size:20px');
+        (expect as any)(result.spec).to.have.property('fontSize', '20px');
+        (expect as any)(result.css).to.contain('font-size:20px');
       });
 
       it('defaults to 14px', () => {
@@ -110,7 +110,7 @@ describe('font', () => {
         expect(result.css).to.contain('font-weight:400');
       });
 
-      it('defaults to \'normal\'', () => {
+      it("defaults to 'normal'", () => {
         const result = fn(null);
         expect(result.spec).to.have.property('fontWeight', 'normal');
         expect(result.css).to.contain('font-weight:normal');
diff --git a/src/legacy/core_plugins/interpreter/public/functions/clog.js b/src/legacy/core_plugins/interpreter/public/functions/clog.ts
similarity index 91%
rename from src/legacy/core_plugins/interpreter/public/functions/clog.js
rename to src/legacy/core_plugins/interpreter/public/functions/clog.ts
index 634d166f5f0bb5..4867726a42d72c 100644
--- a/src/legacy/core_plugins/interpreter/public/functions/clog.js
+++ b/src/legacy/core_plugins/interpreter/public/functions/clog.ts
@@ -20,8 +20,8 @@
 export const clog = () => ({
   name: 'clog',
   help: 'Outputs the context to the console',
-  fn: context => {
-    console.log(context); //eslint-disable-line no-console
+  fn: (context: any) => {
+    console.log(context); // eslint-disable-line no-console
     return context;
   },
 });
diff --git a/src/legacy/core_plugins/interpreter/public/functions/index.js b/src/legacy/core_plugins/interpreter/public/functions/index.ts
similarity index 92%
rename from src/legacy/core_plugins/interpreter/public/functions/index.js
rename to src/legacy/core_plugins/interpreter/public/functions/index.ts
index 38c3920f91bd29..d86f033acb3d13 100644
--- a/src/legacy/core_plugins/interpreter/public/functions/index.js
+++ b/src/legacy/core_plugins/interpreter/public/functions/index.ts
@@ -27,5 +27,12 @@ import { visualization } from './visualization';
 import { visDimension } from './vis_dimension';
 
 export const functions = [
-  clog, esaggs, font, kibana, kibanaContext, range, visualization, visDimension,
+  clog,
+  esaggs,
+  font,
+  kibana,
+  kibanaContext,
+  range,
+  visualization,
+  visDimension,
 ];
diff --git a/src/legacy/core_plugins/interpreter/public/functions/kibana.test.js b/src/legacy/core_plugins/interpreter/public/functions/kibana.test.ts
similarity index 97%
rename from src/legacy/core_plugins/interpreter/public/functions/kibana.test.js
rename to src/legacy/core_plugins/interpreter/public/functions/kibana.test.ts
index 4757b9b12b50da..9f80449ac36be4 100644
--- a/src/legacy/core_plugins/interpreter/public/functions/kibana.test.js
+++ b/src/legacy/core_plugins/interpreter/public/functions/kibana.test.ts
@@ -22,9 +22,9 @@ import { kibana } from './kibana';
 
 describe('interpreter/functions#kibana', () => {
   const fn = functionWrapper(kibana);
-  let context;
-  let initialContext;
-  let handlers;
+  let context: any;
+  let initialContext: any;
+  let handlers: any;
 
   beforeEach(() => {
     context = { timeRange: { from: '0', to: '1' } };
diff --git a/src/legacy/core_plugins/interpreter/public/functions/kibana.js b/src/legacy/core_plugins/interpreter/public/functions/kibana.ts
similarity index 93%
rename from src/legacy/core_plugins/interpreter/public/functions/kibana.js
rename to src/legacy/core_plugins/interpreter/public/functions/kibana.ts
index e0817d8e04b026..37ff337f58b8d4 100644
--- a/src/legacy/core_plugins/interpreter/public/functions/kibana.js
+++ b/src/legacy/core_plugins/interpreter/public/functions/kibana.ts
@@ -24,10 +24,10 @@ export const kibana = () => ({
   type: 'kibana_context',
   context: {},
   help: i18n.translate('interpreter.functions.kibana.help', {
-    defaultMessage: 'Gets kibana global context'
+    defaultMessage: 'Gets kibana global context',
   }),
   args: {},
-  fn(context, args, handlers) {
+  fn(context: any, args: any, handlers: any) {
     const initialContext = handlers.getInitialContext ? handlers.getInitialContext() : {};
 
     if (context.query) {
@@ -45,7 +45,7 @@ export const kibana = () => ({
       type: 'kibana_context',
       query: initialContext.query,
       filters: initialContext.filters,
-      timeRange: timeRange,
+      timeRange,
     };
   },
 });
diff --git a/src/legacy/core_plugins/interpreter/public/functions/kibana_context.js b/src/legacy/core_plugins/interpreter/public/functions/kibana_context.ts
similarity index 87%
rename from src/legacy/core_plugins/interpreter/public/functions/kibana_context.js
rename to src/legacy/core_plugins/interpreter/public/functions/kibana_context.ts
index 7b7294a87831d6..2f2241a3670945 100644
--- a/src/legacy/core_plugins/interpreter/public/functions/kibana_context.js
+++ b/src/legacy/core_plugins/interpreter/public/functions/kibana_context.ts
@@ -24,13 +24,10 @@ export const kibanaContext = () => ({
   name: 'kibana_context',
   type: 'kibana_context',
   context: {
-    types: [
-      'kibana_context',
-      'null',
-    ],
+    types: ['kibana_context', 'null'],
   },
   help: i18n.translate('interpreter.functions.kibana_context.help', {
-    defaultMessage: 'Updates kibana global context'
+    defaultMessage: 'Updates kibana global context',
   }),
   args: {
     q: {
@@ -49,11 +46,11 @@ export const kibanaContext = () => ({
     savedSearchId: {
       types: ['string', 'null'],
       default: null,
-    }
+    },
   },
-  async fn(context, args) {
+  async fn(context: any, args: any) {
     const $injector = await chrome.dangerouslyGetActiveInjector();
-    const savedSearches = $injector.get('savedSearches');
+    const savedSearches = $injector.get('savedSearches') as any;
     const queryArg = args.q ? JSON.parse(args.q) : [];
     let queries = Array.isArray(queryArg) ? queryArg : [queryArg];
     let filters = args.filters ? JSON.parse(args.filters) : [];
@@ -71,7 +68,7 @@ export const kibanaContext = () => ({
     }
 
     if (context.filters) {
-      filters = filters.concat(context.filters).filter(f => !f.meta.disabled);
+      filters = filters.concat(context.filters).filter((f: any) => !f.meta.disabled);
     }
 
     const timeRange = args.timeRange ? JSON.parse(args.timeRange) : context.timeRange;
@@ -79,8 +76,8 @@ export const kibanaContext = () => ({
     return {
       type: 'kibana_context',
       query: queries,
-      filters: filters,
-      timeRange: timeRange,
+      filters,
+      timeRange,
     };
   },
 });
diff --git a/src/legacy/core_plugins/interpreter/public/functions/vis_dimension.js b/src/legacy/core_plugins/interpreter/public/functions/vis_dimension.ts
similarity index 74%
rename from src/legacy/core_plugins/interpreter/public/functions/vis_dimension.js
rename to src/legacy/core_plugins/interpreter/public/functions/vis_dimension.ts
index e1a6c41198bad4..19503dbe03ae98 100644
--- a/src/legacy/core_plugins/interpreter/public/functions/vis_dimension.js
+++ b/src/legacy/core_plugins/interpreter/public/functions/vis_dimension.ts
@@ -22,48 +22,48 @@ import { i18n } from '@kbn/i18n';
 export const visDimension = () => ({
   name: 'visdimension',
   help: i18n.translate('interpreter.function.visDimension.help', {
-    defaultMessage: 'Generates visConfig dimension object'
+    defaultMessage: 'Generates visConfig dimension object',
   }),
   type: 'vis_dimension',
   context: {
-    types: [
-      'kibana_datatable'
-    ],
+    types: ['kibana_datatable'],
   },
   args: {
     accessor: {
       types: ['string', 'number'],
       aliases: ['_'],
       help: i18n.translate('interpreter.function.visDimension.accessor.help', {
-        defaultMessage: 'Column in your dataset to use (either column index or column name)'
+        defaultMessage: 'Column in your dataset to use (either column index or column name)',
       }),
     },
     format: {
       types: ['string'],
-      default: 'string'
+      default: 'string',
     },
     formatParams: {
       types: ['string'],
       default: '"{}"',
-    }
+    },
   },
-  fn: (context, args) => {
-    const accessor = Number.isInteger(args.accessor) ?
-      args.accessor :
-      context.columns.find(c => c.id === args.accessor);
+  fn: (context: any, args: any) => {
+    const accessor = Number.isInteger(args.accessor)
+      ? args.accessor
+      : context.columns.find((c: any) => c.id === args.accessor);
     if (accessor === undefined) {
-      throw new Error(i18n.translate('interpreter.function.visDimension.error.accessor', {
-        defaultMessage: 'Column name provided is invalid'
-      }));
+      throw new Error(
+        i18n.translate('interpreter.function.visDimension.error.accessor', {
+          defaultMessage: 'Column name provided is invalid',
+        })
+      );
     }
 
     return {
       type: 'vis_dimension',
-      accessor: accessor,
+      accessor,
       format: {
         id: args.format,
         params: JSON.parse(args.formatParams),
-      }
+      },
     };
   },
 });
diff --git a/src/legacy/core_plugins/interpreter/public/functions/visualization.js b/src/legacy/core_plugins/interpreter/public/functions/visualization.ts
similarity index 91%
rename from src/legacy/core_plugins/interpreter/public/functions/visualization.js
rename to src/legacy/core_plugins/interpreter/public/functions/visualization.ts
index 7dceeaf6843540..94be78befd3d09 100644
--- a/src/legacy/core_plugins/interpreter/public/functions/visualization.js
+++ b/src/legacy/core_plugins/interpreter/public/functions/visualization.ts
@@ -20,17 +20,16 @@
 import { get } from 'lodash';
 import { i18n } from '@kbn/i18n';
 import chrome from 'ui/chrome';
-import { setup as data } from '../../../data/public/legacy';
-import { start as visualizations } from '../../../visualizations/public/legacy';
-
 import { FilterBarQueryFilterProvider } from 'ui/filter_manager/query_filter';
 import { PersistedState } from 'ui/persisted_state';
+import { setup as data } from '../../../data/public/legacy';
+import { start as visualizations } from '../../../visualizations/public/legacy';
 
 export const visualization = () => ({
   name: 'visualization',
   type: 'render',
   help: i18n.translate('interpreter.functions.visualization.help', {
-    defaultMessage: 'A simple visualization'
+    defaultMessage: 'A simple visualization',
   }),
   args: {
     index: {
@@ -60,17 +59,17 @@ export const visualization = () => ({
     uiState: {
       types: ['string'],
       default: '"{}"',
-    }
+    },
   },
-  async fn(context, args, handlers) {
+  async fn(context: any, args: any, handlers: any) {
     const $injector = await chrome.dangerouslyGetActiveInjector();
-    const Private = $injector.get('Private');
+    const Private = $injector.get('Private') as any;
     const { indexPatterns } = data.indexPatterns;
     const queryFilter = Private(FilterBarQueryFilterProvider);
 
     const visConfigParams = JSON.parse(args.visConfig);
     const schemas = JSON.parse(args.schemas);
-    const visType = visualizations.types.get(args.type || 'histogram');
+    const visType = visualizations.types.get(args.type || 'histogram') as any;
     const indexPattern = args.index ? await indexPatterns.get(args.index) : null;
 
     const uiStateParams = JSON.parse(args.uiState);
@@ -85,7 +84,7 @@ export const visualization = () => ({
         timeRange: get(context, 'timeRange', null),
         query: get(context, 'query', null),
         filters: get(context, 'filters', null),
-        uiState: uiState,
+        uiState,
         inspectorAdapters: handlers.inspectorAdapters,
         queryFilter,
         forceFetch: true,
@@ -95,14 +94,14 @@ export const visualization = () => ({
     if (typeof visType.responseHandler === 'function') {
       if (context.columns) {
         // assign schemas to aggConfigs
-        context.columns.forEach(column => {
+        context.columns.forEach((column: any) => {
           if (column.aggConfig) {
             column.aggConfig.aggConfigs.schemas = visType.schemas.all;
           }
         });
 
         Object.keys(schemas).forEach(key => {
-          schemas[key].forEach(i => {
+          schemas[key].forEach((i: any) => {
             if (context.columns[i] && context.columns[i].aggConfig) {
               context.columns[i].aggConfig.schema = key;
             }
@@ -119,8 +118,8 @@ export const visualization = () => ({
       value: {
         visData: context,
         visType: args.type,
-        visConfig: visConfigParams
-      }
+        visConfig: visConfigParams,
+      },
     };
-  }
+  },
 });
diff --git a/src/legacy/core_plugins/interpreter/public/interpreter.test.js b/src/legacy/core_plugins/interpreter/public/interpreter.test.ts
similarity index 96%
rename from src/legacy/core_plugins/interpreter/public/interpreter.test.js
rename to src/legacy/core_plugins/interpreter/public/interpreter.test.ts
index bd7dc0a47c1240..1de1e8c0cc0598 100644
--- a/src/legacy/core_plugins/interpreter/public/interpreter.test.js
+++ b/src/legacy/core_plugins/interpreter/public/interpreter.test.ts
@@ -24,9 +24,9 @@ jest.mock('ui/new_platform', () => ({
       injectedMetadata: {
         getKibanaVersion: () => '8.0.0',
         getBasePath: () => '/lol',
-      }
-    }
-  }
+      },
+    },
+  },
 }));
 jest.mock('uiExports/interpreter');
 
@@ -38,7 +38,7 @@ jest.mock('@kbn/interpreter/common', () => ({
 const mockInterpreter = {
   interpreter: {
     interpretAst: jest.fn(),
-  }
+  },
 };
 jest.mock('./lib/interpreter', () => ({
   initializeInterpreter: jest.fn().mockReturnValue(Promise.resolve(mockInterpreter)),
@@ -57,9 +57,9 @@ jest.mock('./functions', () => ({ functions: [{}, {}, {}] }));
 jest.mock('./renderers/visualization', () => ({ visualization: {} }));
 
 describe('interpreter/interpreter', () => {
-  let getInterpreter;
-  let interpretAst;
-  let initializeInterpreter;
+  let getInterpreter: any;
+  let interpretAst: any;
+  let initializeInterpreter: any;
 
   beforeEach(() => {
     jest.clearAllMocks();
@@ -117,5 +117,4 @@ describe('interpreter/interpreter', () => {
       expect(mockInterpreter.interpreter.interpretAst).toHaveBeenCalledTimes(2);
     });
   });
-
 });
diff --git a/src/legacy/core_plugins/interpreter/public/interpreter.js b/src/legacy/core_plugins/interpreter/public/interpreter.ts
similarity index 87%
rename from src/legacy/core_plugins/interpreter/public/interpreter.js
rename to src/legacy/core_plugins/interpreter/public/interpreter.ts
index 84e05bb10d9fa6..8ba82d5daf759a 100644
--- a/src/legacy/core_plugins/interpreter/public/interpreter.js
+++ b/src/legacy/core_plugins/interpreter/public/interpreter.ts
@@ -18,6 +18,7 @@
  */
 
 import 'uiExports/interpreter';
+// @ts-ignore
 import { register, registryFactory } from '@kbn/interpreter/common';
 import { initializeInterpreter } from './lib/interpreter';
 import { registries } from './registries';
@@ -27,7 +28,10 @@ import { typeSpecs } from '../../../../plugins/expressions/common';
 
 // Expose kbnInterpreter.register(specs) and kbnInterpreter.registries() globally so that plugins
 // can register without a transpile step.
-global.kbnInterpreter = Object.assign(global.kbnInterpreter || {}, registryFactory(registries));
+(global as any).kbnInterpreter = Object.assign(
+  (global as any).kbnInterpreter || {},
+  registryFactory(registries)
+);
 
 register(registries, {
   types: typeSpecs,
@@ -35,7 +39,7 @@ register(registries, {
   renderers: [visualization],
 });
 
-let interpreterPromise;
+let interpreterPromise: Promise<any> | undefined;
 
 export const getInterpreter = async () => {
   if (!interpreterPromise) {
@@ -44,7 +48,7 @@ export const getInterpreter = async () => {
   return await interpreterPromise;
 };
 
-export const interpretAst = async (...params) => {
+export const interpretAst = async (...params: any) => {
   const { interpreter } = await getInterpreter();
   return await interpreter.interpretAst(...params);
 };
diff --git a/src/legacy/core_plugins/interpreter/public/lib/render_function.js b/src/legacy/core_plugins/interpreter/public/lib/render_function.ts
similarity index 92%
rename from src/legacy/core_plugins/interpreter/public/lib/render_function.js
rename to src/legacy/core_plugins/interpreter/public/lib/render_function.ts
index 04aa05951be70f..76d1f58b661950 100644
--- a/src/legacy/core_plugins/interpreter/public/lib/render_function.js
+++ b/src/legacy/core_plugins/interpreter/public/lib/render_function.ts
@@ -17,7 +17,7 @@
  * under the License.
  */
 
-export function RenderFunction(config) {
+export function RenderFunction(this: any, config: any) {
   // This must match the name of the function that is used to create the `type: render` object
   this.name = config.name;
 
@@ -36,7 +36,7 @@ export function RenderFunction(config) {
   // the function called to render the data
   this.render =
     config.render ||
-    function render(domNode, data, done) {
+    function render(domNode: any, data: any, done: any) {
       done();
     };
 }
diff --git a/src/legacy/core_plugins/interpreter/public/lib/render_functions_registry.js b/src/legacy/core_plugins/interpreter/public/lib/render_functions_registry.ts
similarity index 88%
rename from src/legacy/core_plugins/interpreter/public/lib/render_functions_registry.js
rename to src/legacy/core_plugins/interpreter/public/lib/render_functions_registry.ts
index 60e823baf0fa78..427e7f7454c24e 100644
--- a/src/legacy/core_plugins/interpreter/public/lib/render_functions_registry.js
+++ b/src/legacy/core_plugins/interpreter/public/lib/render_functions_registry.ts
@@ -20,9 +20,9 @@
 import { Registry } from '@kbn/interpreter/common';
 import { RenderFunction } from './render_function';
 
-class RenderFunctionsRegistry extends Registry {
-  wrapper(obj) {
-    return new RenderFunction(obj);
+class RenderFunctionsRegistry extends Registry<any, any> {
+  wrapper(obj: any) {
+    return new (RenderFunction as any)(obj);
   }
 }
 
diff --git a/src/legacy/core_plugins/interpreter/public/renderers/visualization.js b/src/legacy/core_plugins/interpreter/public/renderers/visualization.ts
similarity index 84%
rename from src/legacy/core_plugins/interpreter/public/renderers/visualization.js
rename to src/legacy/core_plugins/interpreter/public/renderers/visualization.ts
index 38fe02436380c7..960e925b132213 100644
--- a/src/legacy/core_plugins/interpreter/public/renderers/visualization.js
+++ b/src/legacy/core_plugins/interpreter/public/renderers/visualization.ts
@@ -19,17 +19,18 @@
 
 import chrome from 'ui/chrome';
 import { visualizationLoader } from 'ui/visualize/loader/visualization_loader';
+// @ts-ignore
 import { VisProvider } from 'ui/visualize/loader/vis';
 
 export const visualization = () => ({
   name: 'visualization',
   displayName: 'visualization',
   reuseDomNode: true,
-  render: async (domNode, config, handlers) => {
+  render: async (domNode: HTMLElement, config: any, handlers: any) => {
     const { visData, visConfig, params } = config;
     const visType = config.visType || visConfig.type;
     const $injector = await chrome.dangerouslyGetActiveInjector();
-    const Private = $injector.get('Private');
+    const Private = $injector.get('Private') as any;
     const Vis = Private(VisProvider);
 
     if (handlers.vis) {
@@ -49,8 +50,10 @@ export const visualization = () => ({
 
     handlers.onDestroy(() => visualizationLoader.destroy());
 
-    await visualizationLoader.render(domNode, handlers.vis, visData, handlers.vis.params, uiState, params).then(() => {
-      if (handlers.done) handlers.done();
-    });
+    await visualizationLoader
+      .render(domNode, handlers.vis, visData, handlers.vis.params, uiState, params)
+      .then(() => {
+        if (handlers.done) handlers.done();
+      });
   },
 });
diff --git a/src/legacy/core_plugins/interpreter/server/lib/__tests__/create_handlers.js b/src/legacy/core_plugins/interpreter/server/lib/__tests__/create_handlers.ts
similarity index 95%
rename from src/legacy/core_plugins/interpreter/server/lib/__tests__/create_handlers.js
rename to src/legacy/core_plugins/interpreter/server/lib/__tests__/create_handlers.ts
index a6e0e13049e1c9..00886630807748 100644
--- a/src/legacy/core_plugins/interpreter/server/lib/__tests__/create_handlers.js
+++ b/src/legacy/core_plugins/interpreter/server/lib/__tests__/create_handlers.ts
@@ -28,13 +28,13 @@ const mockServer = {
   plugins: {
     elasticsearch: {
       getCluster: () => ({
-        callWithRequest: (...args) => Promise.resolve(args),
+        callWithRequest: (...args: any) => Promise.resolve(args),
       }),
     },
   },
   config: () => ({
     has: () => false,
-    get: val => val,
+    get: (val: any) => val,
   }),
   info: {
     uri: 'serveruri',
diff --git a/src/legacy/core_plugins/interpreter/server/lib/create_handlers.js b/src/legacy/core_plugins/interpreter/server/lib/create_handlers.ts
similarity index 88%
rename from src/legacy/core_plugins/interpreter/server/lib/create_handlers.js
rename to src/legacy/core_plugins/interpreter/server/lib/create_handlers.ts
index d4ea9b3dc6180f..6e295d0aecaa59 100644
--- a/src/legacy/core_plugins/interpreter/server/lib/create_handlers.js
+++ b/src/legacy/core_plugins/interpreter/server/lib/create_handlers.ts
@@ -17,7 +17,7 @@
  * under the License.
  */
 
-export const createHandlers = (request, server) => {
+export const createHandlers = (request: any, server: any) => {
   const { callWithRequest } = server.plugins.elasticsearch.getCluster('data');
   const config = server.config();
 
@@ -27,6 +27,6 @@ export const createHandlers = (request, server) => {
       config.has('server.rewriteBasePath') && config.get('server.rewriteBasePath')
         ? `${server.info.uri}${config.get('server.basePath')}`
         : server.info.uri,
-    elasticsearchClient: async (...args) => callWithRequest(request, ...args),
+    elasticsearchClient: async (...args: any) => callWithRequest(request, ...args),
   };
 };
diff --git a/src/legacy/core_plugins/interpreter/server/routes/index.js b/src/legacy/core_plugins/interpreter/server/routes/index.ts
similarity index 95%
rename from src/legacy/core_plugins/interpreter/server/routes/index.js
rename to src/legacy/core_plugins/interpreter/server/routes/index.ts
index 9140f93a9bde64..50385147dd38e6 100644
--- a/src/legacy/core_plugins/interpreter/server/routes/index.js
+++ b/src/legacy/core_plugins/interpreter/server/routes/index.ts
@@ -19,6 +19,6 @@
 
 import { registerServerFunctions } from './server_functions';
 
-export function routes(server) {
+export function routes(server: any) {
   registerServerFunctions(server);
 }
diff --git a/src/legacy/core_plugins/interpreter/server/routes/server_functions.js b/src/legacy/core_plugins/interpreter/server/routes/server_functions.ts
similarity index 84%
rename from src/legacy/core_plugins/interpreter/server/routes/server_functions.js
rename to src/legacy/core_plugins/interpreter/server/routes/server_functions.ts
index b64a9af006e412..740b046610d9e9 100644
--- a/src/legacy/core_plugins/interpreter/server/routes/server_functions.js
+++ b/src/legacy/core_plugins/interpreter/server/routes/server_functions.ts
@@ -18,16 +18,16 @@
  */
 
 import Boom from 'boom';
+import Joi from 'joi';
 import { serializeProvider, API_ROUTE } from '../../common';
 import { createHandlers } from '../lib/create_handlers';
-import Joi from 'joi';
 
 /**
  * Register the Canvas function endopints.
  *
  * @param {*} server - The Kibana server
  */
-export function registerServerFunctions(server) {
+export function registerServerFunctions(server: any) {
   getServerFunctions(server);
   runServerFunctions(server);
 }
@@ -37,7 +37,7 @@ export function registerServerFunctions(server) {
  *
  * @param {*} server - The Kibana server
  */
-function runServerFunctions(server) {
+function runServerFunctions(server: any) {
   server.route({
     method: 'POST',
     path: `${API_ROUTE}/fns`,
@@ -48,19 +48,20 @@ function runServerFunctions(server) {
       },
       validate: {
         payload: Joi.object({
-          functions: Joi.array().items(
-            Joi.object()
-              .keys({
+          functions: Joi.array()
+            .items(
+              Joi.object().keys({
                 id: Joi.number().required(),
                 functionName: Joi.string().required(),
                 args: Joi.object().default({}),
                 context: Joi.any().default(null),
-              }),
-          ).required(),
+              })
+            )
+            .required(),
         }).required(),
       },
     },
-    async handler(req) {
+    async handler(req: any) {
       const handlers = await createHandlers(req, server);
       const { functions } = req.payload;
 
@@ -73,19 +74,19 @@ function runServerFunctions(server) {
       // Send the initial headers.
       res.writeHead(200, {
         'Content-Type': 'text/plain',
-        'Connection': 'keep-alive',
+        Connection: 'keep-alive',
         'Transfer-Encoding': 'chunked',
         'Cache-Control': 'no-cache',
       });
 
       // Write a length-delimited response
-      const streamResult = (result) => {
+      const streamResult = (result: any) => {
         const payload = JSON.stringify(result) + '\n';
         res.write(`${payload.length}:${payload}`);
       };
 
       // Tries to run an interpreter function, and ensures a consistent error payload on failure.
-      const tryFunction = async (id, fnCall) => {
+      const tryFunction = async (id: any, fnCall: any) => {
         try {
           const result = await runFunction(server, handlers, fnCall);
 
@@ -96,7 +97,7 @@ function runServerFunctions(server) {
           return { id, statusCode: 200, result };
         } catch (err) {
           if (Boom.isBoom(err)) {
-            return batchError(id, err.output.payload, err.statusCode);
+            return batchError(id, err.output.payload, (err as any).statusCode);
           } else if (err instanceof Error) {
             return batchError(id, err.message);
           }
@@ -107,7 +108,9 @@ function runServerFunctions(server) {
       };
 
       // Process each function individually, and stream the responses back to the client
-      await Promise.all(functions.map(({ id, ...fnCall }) => tryFunction(id, fnCall).then(streamResult)));
+      await Promise.all(
+        functions.map(({ id, ...fnCall }: any) => tryFunction(id, fnCall).then(streamResult))
+      );
 
       // All of the responses have been written, so we can close the response.
       res.end();
@@ -118,7 +121,7 @@ function runServerFunctions(server) {
 /**
  * A helper function for bundling up errors.
  */
-function batchError(id, message, statusCode = 500) {
+function batchError(id: any, message: any, statusCode = 500) {
   return {
     id,
     statusCode,
@@ -130,7 +133,7 @@ function batchError(id, message, statusCode = 500) {
  * Register the endpoint that returns the list of server-only functions.
  * @param {*} server - The Kibana server
  */
-function getServerFunctions(server) {
+function getServerFunctions(server: any) {
   server.route({
     method: 'GET',
     path: `${API_ROUTE}/fns`,
@@ -147,7 +150,7 @@ function getServerFunctions(server) {
  * @param {*} handlers - The Canvas handlers
  * @param {*} fnCall - Describes the function being run `{ functionName, args, context }`
  */
-async function runFunction(server, handlers, fnCall) {
+async function runFunction(server: any, handlers: any, fnCall: any) {
   const registries = server.plugins.interpreter.registries();
   const { functionName, args, context } = fnCall;
   const types = registries.types.toJS();
diff --git a/src/legacy/core_plugins/interpreter/test_helpers.js b/src/legacy/core_plugins/interpreter/test_helpers.ts
similarity index 86%
rename from src/legacy/core_plugins/interpreter/test_helpers.js
rename to src/legacy/core_plugins/interpreter/test_helpers.ts
index e743b8a09280e2..741cd83bb47fed 100644
--- a/src/legacy/core_plugins/interpreter/test_helpers.js
+++ b/src/legacy/core_plugins/interpreter/test_helpers.ts
@@ -21,8 +21,9 @@ import { mapValues } from 'lodash';
 
 // Takes a function spec and passes in default args,
 // overriding with any provided args.
-export const functionWrapper = fnSpec => {
+export const functionWrapper = (fnSpec: any) => {
   const spec = fnSpec();
   const defaultArgs = mapValues(spec.args, argSpec => argSpec.default);
-  return (context, args, handlers) => spec.fn(context, { ...defaultArgs, ...args }, handlers);
+  return (context: any, args: any, handlers: any) =>
+    spec.fn(context, { ...defaultArgs, ...args }, handlers);
 };
diff --git a/src/legacy/core_plugins/vis_type_markdown/public/markdown_fn.test.ts b/src/legacy/core_plugins/vis_type_markdown/public/markdown_fn.test.ts
index 28021a763b2878..009797905701c5 100644
--- a/src/legacy/core_plugins/vis_type_markdown/public/markdown_fn.test.ts
+++ b/src/legacy/core_plugins/vis_type_markdown/public/markdown_fn.test.ts
@@ -30,7 +30,7 @@ describe('interpreter/functions#markdown', () => {
   };
 
   it('returns an object with the correct structure', async () => {
-    const actual = await fn(undefined, args);
+    const actual = await fn(undefined, args, undefined);
     expect(actual).toMatchSnapshot();
   });
 });
diff --git a/src/legacy/core_plugins/vis_type_metric/public/metric_vis_fn.test.ts b/src/legacy/core_plugins/vis_type_metric/public/metric_vis_fn.test.ts
index 5fe2ac7b7fdf00..fee6dec641842b 100644
--- a/src/legacy/core_plugins/vis_type_metric/public/metric_vis_fn.test.ts
+++ b/src/legacy/core_plugins/vis_type_metric/public/metric_vis_fn.test.ts
@@ -67,7 +67,7 @@ describe('interpreter/functions#metric', () => {
   };
 
   it('returns an object with the correct structure', () => {
-    const actual = fn(context, args);
+    const actual = fn(context, args, undefined);
 
     expect(actual).toMatchSnapshot();
   });
diff --git a/src/legacy/core_plugins/vis_type_table/public/table_vis_fn.test.ts b/src/legacy/core_plugins/vis_type_table/public/table_vis_fn.test.ts
index 2bdebc8a9d19ef..1c1b808ffb0143 100644
--- a/src/legacy/core_plugins/vis_type_table/public/table_vis_fn.test.ts
+++ b/src/legacy/core_plugins/vis_type_table/public/table_vis_fn.test.ts
@@ -76,12 +76,12 @@ describe('interpreter/functions#table', () => {
   });
 
   it('returns an object with the correct structure', async () => {
-    const actual = await fn(context, { visConfig: JSON.stringify(visConfig) });
+    const actual = await fn(context, { visConfig: JSON.stringify(visConfig) }, undefined);
     expect(actual).toMatchSnapshot();
   });
 
   it('calls response handler with correct values', async () => {
-    await fn(context, { visConfig: JSON.stringify(visConfig) });
+    await fn(context, { visConfig: JSON.stringify(visConfig) }, undefined);
     expect(mockResponseHandler).toHaveBeenCalledTimes(1);
     expect(mockResponseHandler).toHaveBeenCalledWith(context, visConfig.dimensions);
   });
diff --git a/src/legacy/core_plugins/vis_type_tagcloud/public/tag_cloud_fn.test.ts b/src/legacy/core_plugins/vis_type_tagcloud/public/tag_cloud_fn.test.ts
index d14871c6bd3375..0365f7840cac42 100644
--- a/src/legacy/core_plugins/vis_type_tagcloud/public/tag_cloud_fn.test.ts
+++ b/src/legacy/core_plugins/vis_type_tagcloud/public/tag_cloud_fn.test.ts
@@ -39,7 +39,7 @@ describe('interpreter/functions#tagcloud', () => {
   };
 
   it('returns an object with the correct structure', () => {
-    const actual = fn(context, visConfig);
+    const actual = fn(context, visConfig, undefined);
     expect(actual).toMatchSnapshot();
   });
 });