diff --git a/packages/api/src/beacon/client/debug.ts b/packages/api/src/beacon/client/debug.ts
index 3e6a8addbd9a..5e54ffa7c0b4 100644
--- a/packages/api/src/beacon/client/debug.ts
+++ b/packages/api/src/beacon/client/debug.ts
@@ -4,7 +4,7 @@ import {HttpStatusCode} from "../../utils/client/httpStatusCode.js";
 import {generateGenericJsonClient, getFetchOptsSerializers, IHttpClient} from "../../utils/client/index.js";
 import {ReturnTypes} from "../../utils/types.js";
 import {StateId} from "../routes/beacon/state.js";
-import {Api, getReqSerializers, getReturnTypes, ReqTypes, routesData, StateFormat} from "../routes/debug.js";
+import {Api, getReqSerializers, getReturnTypes, ReqTypes, routesData, EncodingFormat} from "../routes/debug.js";
 
 // As Jul 2022, it takes up to 3 mins to download states so make this 5 mins for reservation
 const GET_STATE_TIMEOUT_MS = 5 * 60 * 1000;
@@ -31,7 +31,7 @@ export function getClient(_config: ChainForkConfig, httpClient: IHttpClient): Ap
     // TODO: Debug the type issue
     // eslint-disable-next-line @typescript-eslint/ban-ts-comment
     // @ts-expect-error
-    async getState(stateId: string, format?: StateFormat) {
+    async getState(stateId: string, format?: EncodingFormat) {
       if (format === "ssz") {
         const res = await httpClient.arrayBuffer({
           ...fetchOptsSerializers.getState(stateId, format),
@@ -49,7 +49,7 @@ export function getClient(_config: ChainForkConfig, httpClient: IHttpClient): Ap
     // TODO: Debug the type issue
     // eslint-disable-next-line @typescript-eslint/ban-ts-comment
     // @ts-expect-error
-    async getStateV2(stateId: StateId, format?: StateFormat) {
+    async getStateV2(stateId: StateId, format?: EncodingFormat) {
       if (format === "ssz") {
         const res = await httpClient.arrayBuffer({
           ...fetchOptsSerializers.getStateV2(stateId, format),
diff --git a/packages/api/src/beacon/routes/debug.ts b/packages/api/src/beacon/routes/debug.ts
index bedea5b793ef..de28be931a07 100644
--- a/packages/api/src/beacon/routes/debug.ts
+++ b/packages/api/src/beacon/routes/debug.ts
@@ -22,7 +22,7 @@ import {ExecutionOptimistic, StateId} from "./beacon/state.js";
 
 // See /packages/api/src/routes/index.ts for reasoning and instructions to add new routes
 
-export type StateFormat = "json" | "ssz";
+export type EncodingFormat = "json" | "ssz";
 export const mimeTypeSSZ = "application/octet-stream";
 
 const stringType = new StringType();
@@ -56,22 +56,55 @@ type ProtoNodeApiType = ValueOf<typeof protoNodeSszType>;
 export type Api = {
   /**
    * Retrieves all possible chain heads (leaves of fork choice tree).
+   * Depending on `Accept` header it can be returned either as json or as bytes serialized by SSZ
    */
-  getDebugChainHeads(): Promise<ApiClientResponse<{[HttpStatusCode.OK]: {data: {slot: Slot; root: RootHex}[]}}>>;
+  getDebugChainHeads(
+    format?: "json"
+  ): Promise<ApiClientResponse<{[HttpStatusCode.OK]: {data: {slot: Slot; root: RootHex}[]}}>>;
+  getDebugChainHeads(format: "ssz"): Promise<ApiClientResponse<{[HttpStatusCode.OK]: Uint8Array}>>;
+  getDebugChainHeads(
+    format?: EncodingFormat
+  ): Promise<
+    | ApiClientResponse<{[HttpStatusCode.OK]: Uint8Array | {data: {slot: Slot; root: RootHex}[]}}>
+    | ApiClientResponse<{[HttpStatusCode.OK]: {data: {slot: Slot; root: RootHex}[]}}>
+    | ApiClientResponse<{[HttpStatusCode.OK]: Uint8Array}>
+  >;
 
   /**
    * Retrieves all possible chain heads (leaves of fork choice tree).
+   * Depending on `Accept` header it can be returned either as json or as bytes serialized by SSZ
    */
-  getDebugChainHeadsV2(): Promise<
+  getDebugChainHeadsV2(
+    format?: "json"
+  ): Promise<
     ApiClientResponse<{
       [HttpStatusCode.OK]: {data: {slot: Slot; root: RootHex; executionOptimistic: ExecutionOptimistic}[]};
     }>
   >;
+  getDebugChainHeadsV2(
+    format: "ssz"
+  ): Promise<
+    ApiClientResponse<{
+      [HttpStatusCode.OK]: Uint8Array;
+    }>
+  >;
+  getDebugChainHeadsV2(
+    format?: EncodingFormat
+  ): Promise<
+    ApiClientResponse<{
+      [HttpStatusCode.OK]: Uint8Array | {data: {slot: Slot; root: RootHex; executionOptimistic: ExecutionOptimistic}[]};
+    }>
+  >;
 
   /**
    * Dump all ProtoArray's nodes to debug
+   * Depending on `Accept` header it can be returned either as json or as bytes serialized by SSZ
    */
-  getProtoArrayNodes(): Promise<ApiClientResponse<{[HttpStatusCode.OK]: {data: ProtoNodeApiType[]}}>>;
+  getProtoArrayNodes(format?: "json"): Promise<ApiClientResponse<{[HttpStatusCode.OK]: {data: ProtoNodeApiType[]}}>>;
+  getProtoArrayNodes(format: "ssz"): Promise<ApiClientResponse<{[HttpStatusCode.OK]: Uint8Array}>>;
+  getProtoArrayNodes(
+    format?: EncodingFormat
+  ): Promise<ApiClientResponse<{[HttpStatusCode.OK]: Uint8Array | {data: ProtoNodeApiType[]}}>>;
 
   /**
    * Get full BeaconState object
@@ -90,7 +123,7 @@ export type Api = {
   getState(stateId: StateId, format: "ssz"): Promise<ApiClientResponse<{[HttpStatusCode.OK]: Uint8Array}>>;
   getState(
     stateId: StateId,
-    format?: StateFormat
+    format?: EncodingFormat
   ): Promise<
     ApiClientResponse<{
       [HttpStatusCode.OK]: Uint8Array | {data: allForks.BeaconState; executionOptimistic: ExecutionOptimistic};
@@ -116,7 +149,7 @@ export type Api = {
   getStateV2(stateId: StateId, format: "ssz"): Promise<ApiClientResponse<{[HttpStatusCode.OK]: Uint8Array}>>;
   getStateV2(
     stateId: StateId,
-    format?: StateFormat
+    format?: EncodingFormat
   ): Promise<
     ApiClientResponse<{
       [HttpStatusCode.OK]:
diff --git a/packages/api/src/utils/client/client.ts b/packages/api/src/utils/client/client.ts
index 0a8cd95204b1..b835da1a242f 100644
--- a/packages/api/src/utils/client/client.ts
+++ b/packages/api/src/utils/client/client.ts
@@ -10,7 +10,7 @@ import {FetchOpts, HttpError, IHttpClient} from "./httpClient.js";
 
 /**
  * Format FetchFn opts from Fn arguments given a route definition and request serializer.
- * For routes that return only JSOn use @see getGenericJsonClient
+ * For routes that return only JSON see {@link generateGenericJsonClient}
  */
 // eslint-disable-next-line @typescript-eslint/explicit-function-return-type
 export function getFetchOptsSerializer<Fn extends (...args: any) => any, ReqType extends ReqGeneric>(
@@ -34,7 +34,7 @@ export function getFetchOptsSerializer<Fn extends (...args: any) => any, ReqType
 }
 
 /**
- * Generate `getFetchOptsSerializer()` functions for all routes in `Api`
+ * Generate {@link getFetchOptsSerializer()} functions for all routes in `Api`
  */
 // eslint-disable-next-line @typescript-eslint/explicit-function-return-type
 export function getFetchOptsSerializers<