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[hotfix][mcp] Fix MCPTool Jackson deserialization by ignoring unknown properties #532

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Merged
xintongsong merged 1 commit into from
Mar 4, 2026
Merged

[hotfix][mcp] Fix MCPTool Jackson deserialization by ignoring unknown properties #532

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4 changes: 4 additions & 0 deletions api/src/main/java/org/apache/flink/agents/api/tools/Tool.java
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@

package org.apache.flink.agents.api.tools;

import com.fasterxml.jackson.annotation.JsonIgnore;
import org.apache.flink.agents.api.resource.ResourceType;
import org.apache.flink.agents.api.resource.SerializableResource;

Expand All @@ -41,6 +42,7 @@ public final ToolMetadata getMetadata() {
}

/** Return resource type of class. */
@JsonIgnore
@Override
public final ResourceType getResourceType() {
return ResourceType.TOOL;
Expand All @@ -53,11 +55,13 @@ public final ResourceType getResourceType() {
public abstract ToolResponse call(ToolParameters parameters);

/** Get the tool name from metadata. */
@JsonIgnore
public final String getName() {
return metadata.getName();
}

/** Get the tool description from metadata. */
@JsonIgnore
public final String getDescription() {
return metadata.getDescription();
}
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29 changes: 29 additions & 0 deletions integrations/mcp/src/test/java/org/apache/flink/agents/integrations/mcp/MCPToolTest.java
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Expand Up @@ -34,6 +34,35 @@ class MCPToolTest {

private static final String DEFAULT_ENDPOINT = "http://localhost:8000/mcp";

@Test
@DisabledOnJre(JRE.JAVA_11)
@DisplayName(
"JSON round-trip works because @JsonIgnore on Tool getters prevents redundant fields")
void testJsonDeserializationWithDefaultMapper() throws Exception {
ToolMetadata metadata = new ToolMetadata("add", "Add two numbers", "{\"type\":\"object\"}");
MCPServer server = MCPServer.builder(DEFAULT_ENDPOINT).build();
MCPTool original = new MCPTool(metadata, server);

// Use a default ObjectMapper — @JsonIgnore on Tool.getName()/getDescription()/
// getResourceType() prevents these from being serialized, so deserialization
// succeeds without needing @JsonIgnoreProperties on MCPTool.
ObjectMapper mapper = new ObjectMapper();
String json = mapper.writeValueAsString(original);

// Verify redundant top-level fields are not serialized
// (name/description inside metadata are expected)
com.fasterxml.jackson.databind.JsonNode tree = mapper.readTree(json);
assertThat(tree.has("name")).isFalse();
assertThat(tree.has("description")).isFalse();
assertThat(tree.has("resourceType")).isFalse();

MCPTool deserialized = mapper.readValue(json, MCPTool.class);

assertThat(deserialized.getName()).isEqualTo("add");
assertThat(deserialized.getMetadata()).isEqualTo(metadata);
assertThat(deserialized.getMcpServer()).isEqualTo(server);
}

@Test
@DisabledOnJre(JRE.JAVA_11)
@DisplayName("Create MCPTool with metadata and server")
Expand Down