diff --git a/app/core/RPCMethods/RPCMethodMiddleware.test.ts b/app/core/RPCMethods/RPCMethodMiddleware.test.ts
index d3224b6369b..955cc64db1f 100644
--- a/app/core/RPCMethods/RPCMethodMiddleware.test.ts
+++ b/app/core/RPCMethods/RPCMethodMiddleware.test.ts
@@ -1,9 +1,12 @@
-import {
-  JsonRpcEngine,
-  JsonRpcMiddleware,
-} from '@metamask/json-rpc-engine';
-import type { Json, JsonRpcFailure, JsonRpcParams, JsonRpcRequest, JsonRpcResponse, JsonRpcSuccess, } from '@metamask/utils';
-import type { Transaction } from '@metamask/transaction-controller';
+import { JsonRpcEngine, JsonRpcMiddleware } from '@metamask/json-rpc-engine';
+import type {
+  Json,
+  JsonRpcFailure,
+  JsonRpcParams,
+  JsonRpcRequest,
+  JsonRpcResponse,
+  JsonRpcSuccess,
+} from '@metamask/utils';
 import type { ProviderConfig } from '@metamask/network-controller';
 import { providerErrors, rpcErrors } from '@metamask/rpc-errors';
 import Engine from '../Engine';
@@ -827,7 +830,7 @@ describe('getRpcMethodMiddleware', () => {
     it('returns a JSON-RPC error if an error is thrown when adding this transaction', async () => {
       // Omit `from` and `chainId` here to skip validation for simplicity
       // Downcast needed here because `from` is required by this type
-      const mockTransactionParameters = {} as JsonRpcParams
+      const mockTransactionParameters = {} as JsonRpcParams;
       // Transaction fails before returning a result
       mockAddTransaction.mockImplementation(async () => {
         throw new Error('Failed to add transaction');
@@ -840,7 +843,7 @@ describe('getRpcMethodMiddleware', () => {
         jsonrpc,
         id: 1,
         method: 'eth_sendTransaction',
-        params: [mockTransactionParameters]
+        params: [mockTransactionParameters],
       };
       const expectedError = rpcErrors.internal('Failed to add transaction');
 
@@ -857,7 +860,7 @@ describe('getRpcMethodMiddleware', () => {
     it('returns a JSON-RPC error if an error is thrown after approval', async () => {
       // Omit `from` and `chainId` here to skip validation for simplicity
       // Downcast needed here because `from` is required by this type
-      const mockTransactionParameters = {} as JsonRpcParams
+      const mockTransactionParameters = {} as JsonRpcParams;
       setupGlobalState({
         addTransactionResult: Promise.reject(
           new Error('Failed to process transaction'),
diff --git a/app/core/RPCMethods/eth_sendTransaction.test.ts b/app/core/RPCMethods/eth_sendTransaction.test.ts
index 02cfc7eb692..10f1275b211 100644
--- a/app/core/RPCMethods/eth_sendTransaction.test.ts
+++ b/app/core/RPCMethods/eth_sendTransaction.test.ts
@@ -1,6 +1,11 @@
 // eslint-disable-next-line import/no-nodejs-modules
 import { inspect } from 'util';
-import type { JsonRpcRequest, PendingJsonRpcResponse } from '@metamask/utils';
+import type {
+  Json,
+  JsonRpcParams,
+  JsonRpcRequest,
+  PendingJsonRpcResponse,
+} from '@metamask/utils';
 import type {
   Transaction,
   TransactionController,
@@ -40,8 +45,8 @@ jest.mock('../../util/transaction-controller', () => ({
  * @returns The JSON-RPC request.
  */
 function constructSendTransactionRequest(
-  params: unknown,
-): JsonRpcRequest<unknown> & { method: 'eth_sendTransaction' } {
+  params: JsonRpcParams,
+): JsonRpcRequest<JsonRpcParams> & { method: 'eth_sendTransaction' } {
   return {
     jsonrpc: '2.0',
     id: 1,
@@ -55,7 +60,7 @@ function constructSendTransactionRequest(
  *
  * @returns A pending JSON-RPC response.
  */
-function constructPendingJsonRpcResponse(): PendingJsonRpcResponse<unknown> {
+function constructPendingJsonRpcResponse(): PendingJsonRpcResponse<Json> {
   return {
     jsonrpc: '2.0',
     id: 1,
@@ -136,13 +141,17 @@ function getMockAddTransaction({
 describe('eth_sendTransaction', () => {
   it('sends the transaction and returns the resulting hash', async () => {
     const mockAddress = '0x0000000000000000000000000000000000000001';
-    const mockTransactionParameters = { from: mockAddress };
+    const mockTransactionParameters = {
+      from: mockAddress,
+    } as Transaction;
     const expectedResult = 'fake-hash';
     const pendingResult = constructPendingJsonRpcResponse();
 
     await eth_sendTransaction({
       hostname: 'example.metamask.io',
-      req: constructSendTransactionRequest([mockTransactionParameters]),
+      req: constructSendTransactionRequest([
+        mockTransactionParameters as unknown as JsonRpcParams,
+      ]),
       res: pendingResult,
       sendTransaction: getMockAddTransaction({
         expectedTransaction: mockTransactionParameters,
diff --git a/app/core/RPCMethods/eth_sendTransaction.ts b/app/core/RPCMethods/eth_sendTransaction.ts
index b015254a253..6e5f2450ace 100644
--- a/app/core/RPCMethods/eth_sendTransaction.ts
+++ b/app/core/RPCMethods/eth_sendTransaction.ts
@@ -1,6 +1,13 @@
-import type { Json, JsonRpcParams, JsonRpcRequest, PendingJsonRpcResponse } from '@metamask/utils';
+import type {
+  Hex,
+  Json,
+  JsonRpcParams,
+  JsonRpcRequest,
+  PendingJsonRpcResponse,
+} from '@metamask/utils';
 import {
   TransactionController,
+  Transaction,
   WalletDevice,
 } from '@metamask/transaction-controller';
 import { rpcErrors } from '@metamask/rpc-errors';
@@ -46,10 +53,10 @@ const hasProperty = <
 ): objectToCheck is ObjectToCheck & Record<Property, unknown> =>
   Object.hasOwnProperty.call(objectToCheck, name);
 
-type SendArgs = {
+interface SendArgs {
   from: string;
-  chainId?: number;
-};
+  chainId?: Hex;
+}
 
 /**
  * Handle a `eth_sendTransaction` request.
@@ -71,7 +78,9 @@ async function eth_sendTransaction({
   validateAccountAndChainId,
 }: {
   hostname: string;
-  req: JsonRpcRequest<SendArgs[]> & { method: 'eth_sendTransaction' };
+  req: JsonRpcRequest<[Transaction & JsonRpcParams]> & {
+    method: 'eth_sendTransaction';
+  };
   res: PendingJsonRpcResponse<Json>;
   sendTransaction: TransactionController['addTransaction'];
   validateAccountAndChainId: (args: SendArgs) => Promise<void>;
diff --git a/app/core/RPCMethods/wallet_watchAsset.ts b/app/core/RPCMethods/wallet_watchAsset.ts
index 05ed911ccd7..3a78dd9c024 100644
--- a/app/core/RPCMethods/wallet_watchAsset.ts
+++ b/app/core/RPCMethods/wallet_watchAsset.ts
@@ -11,7 +11,10 @@ import {
 } from '../../constants/error';
 import { selectChainId } from '../../selectors/networkController';
 import { isValidAddress } from 'ethereumjs-util';
-import { JsonRpcRequest, PendingJsonRpcResponse } from '@metamask/json-rpc-engine';
+import {
+  JsonRpcRequest,
+  PendingJsonRpcResponse,
+} from '@metamask/json-rpc-engine';
 
 const wallet_watchAsset = async ({
   req,
diff --git a/app/core/SanitizationMiddleware.ts b/app/core/SanitizationMiddleware.ts
index 02ded3ed0ba..d49e6b39107 100644
--- a/app/core/SanitizationMiddleware.ts
+++ b/app/core/SanitizationMiddleware.ts
@@ -40,7 +40,9 @@ export const permittedKeys = [
  * @param parameter - The parameter to sanitize.
  * @returns The given parameter containing just permitted keys.
  */
-function sanitizeRpcParameter(parameter: Record<PropertyKey, unknown>): Record<string, Json> {
+function sanitizeRpcParameter(
+  parameter: Record<PropertyKey, unknown>,
+): Record<string, Json> {
   return permittedKeys.reduce<Record<string, Json>>((copy, permitted) => {
     if (permitted in parameter) {
       const value = parameter[permitted];