diff --git a/src/entities/project-entities.ts b/src/entities/project-entities.ts
index d56516d..c3cbbf5 100644
--- a/src/entities/project-entities.ts
+++ b/src/entities/project-entities.ts
@@ -1,3 +1,4 @@
+/** Each project is like a "folder" to store multiple specs of requests. */
 export interface Project {
   readonly uuid: string;
   readonly name: string;
@@ -5,11 +6,13 @@ export interface Project {
   readonly specs: ProjectRequestSpec[];
 }
 
+/** TODO: to organize requests as "subfolders" in a project. */
 export interface ProjectSection {
   readonly uuid: string;
   readonly name: string;
 }
 
+/** User specification of how its request looks like. */
 export interface ProjectRequestSpec {
   readonly uuid: string;
   readonly url: string;
@@ -18,6 +21,7 @@ export interface ProjectRequestSpec {
   readonly body: string;
 }
 
+/** Data structure of HTTP headers specified in a `ProjectRequestSpec`, can be toggled. */
 export interface ProjectRequestSpecHeader {
   readonly key: string;
   readonly value: string;
diff --git a/src/entities/runtime-entities.ts b/src/entities/runtime-entities.ts
index 28526d8..2ca6d9f 100644
--- a/src/entities/runtime-entities.ts
+++ b/src/entities/runtime-entities.ts
@@ -1,20 +1,46 @@
+/**
+ * Representation of each spec being put to exectution,
+ * become concrete and not only a spec.
+ */
 export interface RuntimeState {
+  /**
+   * `"idle"` is waiting runtime didn't start yet.
+   * `"running"` is request being performed right now.
+   * `"success"` is request finished, responded with ok status.
+   * `"unsuccess"` is request finished, responded with not ok status.
+   * `"error"` for when the request didn't even reach the server.
+   */
   readonly step: "idle" | "running" | "success" | "unsuccess" | "error";
-  readonly text: string;
-  readonly status: number;
+  /** Observability snapshot of the request. With blank values while `step="idle"`. */
+  readonly request: RequestInfo;
+  /** Observability of the response. With blank values if there wasn't a server response yet. */
+  readonly response: ResponseInfo;
+  /** Any exception unrelated to the direct 1:1 request-response relation (see `step="error"`). */
+  readonly errorMessage: string;
+  /** Useful metadata for performance visibility. */
   readonly startedAt: number;
+  /** Useful metadata for performance visibility. */
   readonly finishedAt: number;
 }
 
+/**
+ * Applied final data used to make a real request run.
+ *
+ * However, due to browser policies, the actual request headers for example are not
+ * fully acessible. There's no API available to preview what the browser itself intercepted.
+ */
 export interface RequestInfo {
   readonly url: string;
   readonly method: string;
   readonly body: string;
-  readonly headers: { [key: string]: string };
+  readonly headers: Array<{ key: string; value: string }>;
 }
 
+/**
+ * Response received by the server after a request.
+ */
 export interface ResponseInfo {
   readonly status: number;
   readonly body: string;
-  readonly headers: { [key: string]: string };
+  readonly headers: Array<{ key: string; value: string }>;
 }
diff --git a/src/features/project-workspace/ProjectWorkspacePage.tsx b/src/features/project-workspace/ProjectWorkspacePage.tsx
index 90436fe..c109fcd 100644
--- a/src/features/project-workspace/ProjectWorkspacePage.tsx
+++ b/src/features/project-workspace/ProjectWorkspacePage.tsx
@@ -24,6 +24,11 @@ import {
 } from "@/components/ui/dialog";
 import { RequestsSpecsContextProvider } from "./RequestsSpecsContextProvider";
 import { useRequestsSpecs } from "./RequestsSpecsContext";
+import {
+  RuntimeState,
+  RequestInfo,
+  ResponseInfo,
+} from "@/entities/runtime-entities";
 import { Input } from "@/components/ui/input";
 import {
   Select,
@@ -33,7 +38,6 @@ import {
   SelectValue,
 } from "@/components/ui/select";
 import { Progress } from "@/components/ui/progress";
-import { RuntimeState } from "@/entities/runtime-entities";
 
 export function ProjectWorkspacePage() {
   const params = useParams();
@@ -190,36 +194,49 @@ function RequestSpecEditor(props: {
 
   const [runtime, setRuntime] = useState<RuntimeState>({
     step: "idle",
-    text: "",
-    status: 0,
+    request: {
+      url: "",
+      method: "",
+      body: "",
+      headers: [],
+    },
+    response: {
+      status: 0,
+      body: "",
+      headers: [],
+    },
+    errorMessage: "",
     startedAt: 0,
     finishedAt: 0,
   });
 
-  const begin = () =>
+  const begin = (request: RequestInfo) =>
     setRuntime({
       step: "running",
-      text: "",
-      status: 0,
+      request,
+      response: {
+        status: 0,
+        body: "",
+        headers: [],
+      },
+      errorMessage: "",
       startedAt: Date.now(),
       finishedAt: 0,
     });
 
-  const success = (text: string, status: number) =>
+  const success = (response: ResponseInfo) =>
     setRuntime((updatingRuntime) => ({
       ...updatingRuntime,
       step: "success",
-      status,
-      text,
+      response,
       finishedAt: Date.now(),
     }));
 
-  const unsuccess = (text: string, status: number) =>
+  const unsuccess = (response: ResponseInfo) =>
     setRuntime((updatingRuntime) => ({
       ...updatingRuntime,
       step: "unsuccess",
-      text,
-      status,
+      response,
       finishedAt: Date.now(),
     }));
 
@@ -232,16 +249,35 @@ function RequestSpecEditor(props: {
     }));
 
   const runSpec = async (running: { method: string; url: string }) => {
-    begin();
+    const requestInfo: RequestInfo = {
+      url: running.url,
+      method: running.method,
+      body: "",
+      headers: spec?.headers.length
+        ? spec.headers.filter((h) => h.isEnabled)
+        : [],
+    };
+
+    begin(requestInfo);
     try {
       const response = await fetch(running.url, {
-        method: running.method,
+        method: requestInfo.method,
+        headers: requestInfo.headers.reduce(
+          (headers, header) => ({ ...headers, [header.key]: header.value }),
+          {}
+        ),
       });
-      const text = await response.text();
+      const responseInfo: ResponseInfo = {
+        status: response.status,
+        body: await response.text(),
+        headers: Object.entries(response.headers).map(
+          ([key, value]: [string, string]) => ({ key, value })
+        ),
+      };
       if (response.ok) {
-        success(text, response.status);
+        success(responseInfo);
       } else {
-        unsuccess(text, response.status);
+        unsuccess(responseInfo);
       }
     } catch (exception) {
       error((exception as Error).message);
@@ -308,11 +344,12 @@ function RequestSpecEditor(props: {
         {runtime.step === "success" && (
           <>
             <p className="text-green-400 mb-3">
-              <strong>HTTP success:</strong> <code>{runtime.status}</code>
+              <strong>HTTP success:</strong>{" "}
+              <code>{runtime.response.status}</code>
             </p>
-            {runtime.text ? (
+            {runtime.response.body ? (
               <p>
-                <code>{runtime.text}</code>
+                <code>{runtime.response.body}</code>
               </p>
             ) : (
               <p>
@@ -324,11 +361,12 @@ function RequestSpecEditor(props: {
         {runtime.step === "unsuccess" && (
           <>
             <p className="text-red-400 mb-3">
-              <strong>HTTP bad code:</strong> <code>{runtime.status}</code>
+              <strong>HTTP bad code:</strong>{" "}
+              <code>{runtime.response.status}</code>
             </p>
-            {runtime.text ? (
+            {runtime.response.body ? (
               <p>
-                <code>{runtime.text}</code>
+                <code>{runtime.response.body}</code>
               </p>
             ) : (
               <p>
@@ -340,9 +378,10 @@ function RequestSpecEditor(props: {
         {runtime.step === "error" && (
           <>
             <p className="text-red-400 mb-3">Error.</p>
-            {runtime.text ? (
+            {runtime.errorMessage ? (
               <p>
-                <strong>Browser reason:</strong> <code>{runtime.text}</code>
+                <strong>Browser reason:</strong>{" "}
+                <code>{runtime.errorMessage}</code>
               </p>
             ) : (
               <p>