fix(skills): remove unregistered script tool from default instructions

Author: quifox

core/src/main/java/com/google/adk/tools/skills/SkillToolset.java

@@ -56,7 +56,6 @@ public class SkillToolset implements BaseToolset {
       1. If a skill seems relevant to the current user query, you MUST use the `load_skill` tool with `skill_name="<SKILL_NAME>"` to read its full instructions before proceeding.
       2. Once you have read the instructions, follow them exactly as documented before replying to the user. For example, If the instruction lists multiple steps, please make sure you complete all of them in order.
       3. The `load_skill_resource` tool is for viewing files within a skill's directory (e.g., `references/*`, `assets/*`, `scripts/*`). Do NOT use other tools to access these files.
-      4. Use `run_skill_script` to run scripts from a skill's `scripts/` directory. Use `load_skill_resource` to view script content first if needed.
       """;
 
   private final SkillSource skillSource;

core/src/test/java/com/google/adk/tools/skills/SkillToolsetTest.java

@@ -31,6 +31,7 @@
 import com.google.common.truth.Correspondence;
 import io.reactivex.rxjava3.core.Flowable;
 import java.util.List;
+import java.util.regex.Pattern;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
@@ -140,4 +141,29 @@ public void close() {}
       baseToolset.processLlmRequest(LlmRequest.builder(), mock(ToolContext.class)).blockingAwait();
     }
   }
+
+  @Test
+  public void processLlmRequest_defaultInstructionOnlyMentionsRegisteredTools() throws Exception {
+    SkillSource skillSource =
+        InMemorySkillSource.builder()
+            .skill("test-skill")
+            .frontmatter(Frontmatter.builder().name("test-skill").description("test skill").build())
+            .instructions("Test instructions")
+            .build();
+    try (SkillToolset toolSet = new SkillToolset(skillSource)) {
+      LlmRequest.Builder requestBuilder = LlmRequest.builder();
+      toolSet.processLlmRequest(requestBuilder, mock(ToolContext.class)).blockingAwait();
+      List<String> availableTools =
+          toolSet.getTools(null).toList().blockingGet().stream().map(BaseTool::name).toList();
+      List<String> mentionedTools =
+          Pattern.compile("`([a-z_]+)`")
+              .matcher(requestBuilder.build().getSystemInstructions().get(0))
+              .results()
+              .map(match -> match.group(1))
+              .distinct()
+              .toList();
+      assertThat(mentionedTools).isNotEmpty();
+      assertThat(availableTools).containsAtLeastElementsIn(mentionedTools);
+    }
+  }
 }