Offer an LLM node's required tools only once it has MCP servers

The tools a node must have used successfully are checked by the loop
that bound MCP servers start; a node without one runs a single call and
never looks at them. The editor showed the field regardless, inviting a
setting that could do nothing. It now appears once the node has an MCP
server, through a visible-when rule that can say "once this holds
something" - the same present rule enabled-when already had.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/main/java/it/cnr/isti/workflow/manager/blocks/configurations/JsonSchemaProducer.java

@@ -1449,6 +1449,9 @@ public class JsonSchemaProducer {
                     equalsAny.add(value);
                 }
             }
+            if (dependency.present()) {
+                visibleWhen.put("present", true);
+            }
         }
     }
 

src/main/java/it/cnr/isti/workflow/manager/blocks/configurations/LLMBlockConfiguration.java

@@ -18,6 +18,7 @@ import it.cnr.isti.workflow.manager.configurations.annotations.UiDescription;
 import it.cnr.isti.workflow.manager.configurations.annotations.UiLabel;
 import it.cnr.isti.workflow.manager.configurations.annotations.UiOrder;
 import it.cnr.isti.workflow.manager.configurations.annotations.UiUniqueItemsBy;
+import it.cnr.isti.workflow.manager.configurations.annotations.UiVisibleWhen;
 import it.cnr.isti.workflow.manager.llms.LLMDescriptor;
 import it.cnr.isti.workflow.manager.mcp.MCPToolServerBinding;
 import it.cnr.isti.workflow.manager.skills.SkillBinding;
@@ -75,6 +76,8 @@ public class LLMBlockConfiguration extends BlockConfiguration<LLMBlockType> {
     @Structural
     @Size(max = 16)
     @UiOrder(70)
+    // Checked only by the loop MCP servers start, so without one there is nothing it could apply to.
+    @UiVisibleWhen(field = "mcpServers", present = true)
     @UiLabel("Required successful MCP tools")
     @UiDescription("Tool names that must each complete successfully before this node can finish. Use this for agents that must prove work, for example start_service, browser_navigate and browser_snapshot.")
     @JsonProperty(required = false)

src/main/java/it/cnr/isti/workflow/manager/configurations/annotations/UiVisibleWhen.java

@@ -26,4 +26,6 @@ public @interface UiVisibleWhen {
     String equals() default "";
 
     String[] equalsAny() default {};
+    /** Shown only once {@link #field()} holds something: a text that is not blank, a list with an item. */
+    boolean present() default false;
 }

src/test/java/it/cnr/isti/workflow/manager/blocks/configurations/LLMBlockSchemaTest.java

@@ -0,0 +1,33 @@
+// SPDX-FileCopyrightText: 2025-2026 Lucio Lelii <lucio.lelii@isti.cnr.it> - ISTI-CNR
+// SPDX-License-Identifier: AGPL-3.0-or-later
+// Attribution term under AGPL-3.0 section 7(b): see LICENSE-ADDENDUM.
+
+package it.cnr.isti.workflow.manager.blocks.configurations;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.TestPropertySource;
+
+import tools.jackson.databind.JsonNode;
+
+/** What the editor is told about an LLM node's fields. */
+@SpringBootTest
+@TestPropertySource(locations = "classpath:test.properties")
+class LLMBlockSchemaTest {
+
+    @Autowired
+    private JsonSchemaProducer schemaProducer;
+
+    @Test
+    void theRequiredToolsAreOfferedOnlyToANodeThatHasMcpServersToCall() {
+        JsonNode schema = schemaProducer.generateSchemaNode(LLMBlockConfiguration.class);
+
+        JsonNode visibleWhen = schema.get("properties").get("requiredSuccessfulMcpTools").get("x-ui-visible-when");
+
+        assertEquals("mcpServers", visibleWhen.get("field").asText());
+        assertEquals(true, visibleWhen.get("present").asBoolean());
+    }
+}