diff --git a/examples/agents/granite/granite_wiki_bee.ts b/examples/agents/granite/granite_wiki_bee.ts
index 6a0e7abb..6424bab4 100644
--- a/examples/agents/granite/granite_wiki_bee.ts
+++ b/examples/agents/granite/granite_wiki_bee.ts
@@ -63,7 +63,7 @@ function wikipediaRetrivalTool(passageSize: number, overlap: number, maxResults:
       query: input.query,
       documents: output.results.flatMap((document) =>
         Array.from(
-          splitString(document.fields.markdown as string, {
+          splitString(document.fields.markdown ?? "", {
             size: passageSize * charsPerToken,
             overlap: overlap * charsPerToken,
           }),
diff --git a/examples/tools/custom/piping.ts b/examples/tools/custom/piping.ts
index f4b7dbac..9d6bf88e 100644
--- a/examples/tools/custom/piping.ts
+++ b/examples/tools/custom/piping.ts
@@ -26,7 +26,7 @@ const wikipediaWithSimilarity = wikipedia
   .pipe(similarity, (input, output) => ({
     query: input.query,
     documents: output.results.flatMap((document) =>
-      Array.from(splitString(document.fields.markdown as string, { size: 1000, overlap: 50 })).map(
+      Array.from(splitString(document.fields.markdown ?? "", { size: 1000, overlap: 50 })).map(
         (chunk) => ({
           text: chunk,
           source: document,
diff --git a/src/internals/helpers/promise.ts b/src/internals/helpers/promise.ts
index edc94590..41f37b27 100644
--- a/src/internals/helpers/promise.ts
+++ b/src/internals/helpers/promise.ts
@@ -69,7 +69,7 @@ export async function* emitterToGenerator<T, R>(fn: EmitterToGeneratorFn<T, R>)
 
 export async function asyncProperties<T extends NonNullable<unknown>>(
   obj: T,
-): Promise<{ [K in keyof T]: T[K] extends Promise<infer P> ? P : T[K] }> {
+): Promise<{ [K in keyof T]: Awaited<T[K]> }> {
   return Object.fromEntries(
     await Promise.all(Object.entries(obj).map(async ([key, value]) => [key, await value])),
   );
diff --git a/src/tools/search/wikipedia.ts b/src/tools/search/wikipedia.ts
index 908942bd..e2f86f0a 100644
--- a/src/tools/search/wikipedia.ts
+++ b/src/tools/search/wikipedia.ts
@@ -14,10 +14,11 @@
  * limitations under the License.
  */
 
+import type { Page, pageFunctions, searchOptions } from "wikipedia";
 import wiki from "wikipedia";
 import { Cache } from "@/cache/decoratorCache.js";
 import * as R from "remeda";
-import type { Page, pageFunctions, searchOptions } from "wikipedia";
+import { keys, mapValues } from "remeda";
 import { ArrayKeys, Common } from "@/internals/types.js";
 import {
   SearchToolOptions,
@@ -27,11 +28,10 @@ import {
 } from "./base.js";
 import { asyncProperties } from "@/internals/helpers/promise.js";
 import { z } from "zod";
-import { ToolEmitter, Tool, ToolInput } from "@/tools/base.js";
+import { Tool, ToolEmitter, ToolInput } from "@/tools/base.js";
 import Turndown from "turndown";
 // @ts-expect-error missing types
 import turndownPlugin from "joplin-turndown-plugin-gfm";
-import { keys, mapValues } from "remeda";
 import stringComparison from "string-comparison";
 import { pageResult } from "wikipedia/dist/resultTypes.js";
 import { Emitter } from "@/emitter/emitter.js";
@@ -80,8 +80,12 @@ export interface WikipediaToolRunOptions extends SearchToolRunOptions {
   output?: OutputOptions;
 }
 
+type PageWithMarkdown = Page & { markdown: () => Promise<string> };
+
+type ResultFields = { [K in keyof PageFunctions]: Awaited<ReturnType<PageWithMarkdown[K]>> };
+
 export interface WikipediaToolResult extends SearchToolResult {
-  fields: Partial<Record<keyof PageFunctions, unknown>>;
+  fields: Partial<ResultFields>;
 }
 
 export class WikipediaToolOutput extends SearchToolOutput<WikipediaToolResult> {
@@ -382,7 +386,7 @@ export class WikipediaTool extends Tool<
             mapValues(runOptions?.extraction?.fields ?? {}, (value, key) =>
               this._mappers[key](page, runOptions)
                 .then((response) => (value.transform ? value.transform(response) : response))
-                .catch(() => null),
+                .catch(() => undefined),
             ),
           ),
         });