diff --git a/package-lock.json b/package-lock.json
index 56fb93a..bbc6c80 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -880,6 +880,7 @@
       "resolved": "https://registry.npmjs.org/@opentelemetry/api/-/api-1.9.0.tgz",
       "integrity": "sha512-3giAOQvZiH5F9bMlMiv8+GSPMeqg0dbaeo58/0SlA9sxSqZhnUtxzX9/2FzyhS9sWQf5S0GJE0AKBrFqjpeYcg==",
       "license": "Apache-2.0",
+      "peer": true,
       "engines": {
         "node": ">=8.0.0"
       }
@@ -993,6 +994,7 @@
       "resolved": "https://registry.npmjs.org/@opentelemetry/core/-/core-2.5.0.tgz",
       "integrity": "sha512-ka4H8OM6+DlUhSAZpONu0cPBtPPTQKxbxVzC4CzVx5+K4JnroJVBtDzLAMx4/3CDTJXRvVFhpFjtl4SaiTNoyQ==",
       "license": "Apache-2.0",
+      "peer": true,
       "dependencies": {
         "@opentelemetry/semantic-conventions": "^1.29.0"
       },
@@ -3051,6 +3053,7 @@
       "resolved": "https://registry.npmjs.org/acorn/-/acorn-8.15.0.tgz",
       "integrity": "sha512-NZyJarBfL7nWwIq+FDL6Zp/yHEhePMNnnJ0y3qfieCrmNvYct8uvtiV41UvlSe6apAfk0fY1FbWx+NwfmpvtTg==",
       "license": "MIT",
+      "peer": true,
       "bin": {
         "acorn": "bin/acorn"
       },
@@ -3709,6 +3712,7 @@
       "resolved": "https://registry.npmjs.org/express/-/express-5.2.1.tgz",
       "integrity": "sha512-hIS4idWWai69NezIdRt2xFVofaF4j+6INOpJlVOLDO8zXGpUVEVzIYk12UUi2JzjEzWL3IOAxcTubgz9Po0yXw==",
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "accepts": "^2.0.0",
         "body-parser": "^2.2.1",
@@ -4018,6 +4022,7 @@
       "resolved": "https://registry.npmjs.org/hono/-/hono-4.11.9.tgz",
       "integrity": "sha512-Eaw2YTGM6WOxA6CXbckaEvslr2Ne4NFsKrvc0v97JD5awbmeBLO5w9Ho9L9kmKonrwF9RJlW6BxT1PVv/agBHQ==",
       "license": "MIT",
+      "peer": true,
       "engines": {
         "node": ">=16.9.0"
       }
@@ -4657,6 +4662,7 @@
       "integrity": "sha512-5gTmgEY/sqK6gFXLIsQNH19lWb4ebPDLA4SdLP7dsWkIXHWlG66oPuVvXSGFPppYZz8ZDZq0dYYrbHfBCVUb1Q==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "engines": {
         "node": ">=12"
       },
@@ -5370,6 +5376,7 @@
       "integrity": "sha512-w+N7Hifpc3gRjZ63vYBXA56dvvRlNWRczTdmCBBa+CotUzAPf5b7YMdMR/8CQoeYE5LX3W4wj6RYTgonm1b9DA==",
       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "esbuild": "^0.27.0",
         "fdir": "^6.5.0",
@@ -5705,6 +5712,7 @@
       "resolved": "https://registry.npmjs.org/zod/-/zod-4.3.6.tgz",
       "integrity": "sha512-rftlrkhHZOcjDwkGlnUtZZkvaPHCsDATp4pGpuOOMDaTdDDXF91wuVDJoWoPsKX/3YPQ5fHuF3STjcYyKr+Qhg==",
       "license": "MIT",
+      "peer": true,
       "funding": {
         "url": "https://github.com/sponsors/colinhacks"
       }
diff --git a/test/test-utils.ts b/test/test-utils.ts
index a76b4a0..ebed907 100644
--- a/test/test-utils.ts
+++ b/test/test-utils.ts
@@ -1,5 +1,41 @@
 import { spawn, ChildProcess } from "child_process";
 
+/**
+ * A single MCP tool description returned by the tools/list method.
+ * This is a minimal structural type to avoid using `any` while allowing
+ * the response to include additional properties.
+ */
+export interface McpToolDescription {
+  name: string;
+  description?: string;
+  // Allow additional properties without losing type safety.
+  [key: string]: unknown;
+}
+
+/**
+ * JSON-RPC 2.0 response for the tools/list method,
+ * when returned as a standard JSON HTTP response.
+ */
+export interface ListMcpToolsResponse {
+  jsonrpc: "2.0";
+  id: number | string | null;
+  result?: {
+    tools?: McpToolDescription[];
+    [key: string]: unknown;
+  };
+  error?: {
+    code: number;
+    message: string;
+    data?: unknown;
+  };
+}
+
+/**
+ * Response shape when the tools/list call is delivered via
+ * Server-Sent Events and parsed by `parseSSEResponse`.
+ */
+export type ListMcpToolsSseResponse = SSEResponseData;
+
 /**
  * Wait for server to be ready by polling health endpoint
  */
@@ -41,7 +77,9 @@ export async function isServerRunning(port: number): Promise<boolean> {
 /**
  * Parse SSE (Server-Sent Events) response
  */
-export function parseSSEResponse(sseText: string): any {
+export type SSEResponseData = Record<string, unknown>;
+
+export function parseSSEResponse(sseText: string): SSEResponseData {
   const lines = sseText.trim().split("\n");
   for (const line of lines) {
     if (line.startsWith("data: ")) {
@@ -158,6 +196,41 @@ export async function initializeMCPSession(
   return sessionId;
 }
 
+/**
+ * JSON-RPC response types for MCP tool calls
+ */
+interface McpToolError {
+  code: number;
+  message: string;
+  data?: unknown;
+}
+
+interface McpToolSuccessResult {
+  jsonrpc: "2.0";
+  id: number | string | null;
+  result: unknown;
+}
+
+interface McpToolErrorResult {
+  jsonrpc: "2.0";
+  id: number | string | null;
+  error: McpToolError;
+}
+
+type McpToolResponse = McpToolSuccessResult | McpToolErrorResult;
+
+/**
+ * Counter for generating sequential JSON-RPC IDs for deterministic testing
+ */
+let nextJsonRpcId = 1;
+
+/**
+ * Reset the JSON-RPC ID counter. Call this in test setup/teardown to ensure test isolation.
+ */
+export function resetJsonRpcId(): void {
+  nextJsonRpcId = 1;
+}
+
 /**
  * Call MCP tool
  */
@@ -165,8 +238,8 @@ export async function callMCPTool(
   baseUrl: string,
   sessionId: string,
   toolName: string,
-  args: any
-): Promise<any> {
+  args: unknown
+): Promise<McpToolResponse | SSEResponseData> {
   const response = await fetch(baseUrl, {
     method: "POST",
     headers: {
@@ -181,7 +254,7 @@ export async function callMCPTool(
         name: toolName,
         arguments: args,
       },
-      id: Math.floor(Math.random() * 10000),
+      id: nextJsonRpcId++,
     }),
   });
 
@@ -195,7 +268,8 @@ export async function callMCPTool(
     const text = await response.text();
     return parseSSEResponse(text);
   } else {
-    return response.json();
+    const jsonResponse = await response.json();
+    return jsonResponse as McpToolResponse;
   }
 }
 
@@ -205,7 +279,7 @@ export async function callMCPTool(
 export async function listMCPTools(
   baseUrl: string,
   sessionId: string
-): Promise<any> {
+): Promise<ListMcpToolsResponse | ListMcpToolsSseResponse> {
   const response = await fetch(baseUrl, {
     method: "POST",
     headers: {
@@ -230,6 +304,7 @@ export async function listMCPTools(
     const text = await response.text();
     return parseSSEResponse(text);
   } else {
-    return response.json();
+    const jsonResponse = await response.json();
+    return jsonResponse as ListMcpToolsResponse;
   }
 }