update readme

Author: alexcheng1982

README.md

@@ -2,3 +2,23 @@
 
 [![build](https://github.com/JavaAIDev/usda-fooddata-central-mcp/actions/workflows/build.yaml/badge.svg)](https://github.com/JavaAIDev/usda-fooddata-central-mcp/actions/workflows/build.yaml)
 
+Use environment variable `UDSA_FDC_API_KEY` to provide an API key. The default `DEMO_KEY` is used when not provided.
+
+The config below starts the server using a container image.
+
+```json
+{
+  "mcpServers": {
+    "amap": {
+      "command": "docker",
+      "args": [
+        "run",
+        "-i",
+        "-e",
+        "UDSA_FDC_API_KEY=YOUR_AMAP_API_KEY",
+        "ghcr.io/javaaidev/usda-fooddata-central-mcp-server:1.0.0"
+      ]
+    }
+  }
+}
+```

src/main/java/com/javaaidev/usdafdc/mcp/AppConfiguration.java

@@ -25,7 +25,7 @@ public ServerCapabilities.Builder serverCapabilitiesBuilder() {
   }
 
   @Bean
-  public FileCacheService fileCacheAspect() {
+  public FileCacheService fileCacheService() {
     return new FileCacheService();
   }
 

src/main/java/com/javaaidev/usdafdc/mcp/cache/FileCacheService.java

@@ -24,7 +24,7 @@ public FileCacheService() {
       Files.createDirectories(cacheDir);
       LOGGER.info("Cache dir is {}", cacheDir);
     } catch (IOException e) {
-      LOGGER.error("Failed to create cache dir", e);
+      LOGGER.error("Failed to create cache dir: {}", cacheDir, e);
     }
   }