Vino1016 opened a new issue, #578: URL: https://github.com/apache/flink-agents/issues/578
### Search before asking - [x] I searched in the [issues](https://github.com/apache/flink-agents/issues) and found nothing similar. ### Description Flink Agents Java MCP client crashes when deserializing prompt arguments if the required field is omitted by the MCP server. According to the MCP specification, PromptArgument.required is optional (required?: boolean). MCP servers may omit it, in which case Jackson deserializes it as null. In org.apache.flink.agents.integrations.mcp.MCPServer#listPrompts, Flink Agents unconditionally passes arg.required() to new MCPPrompt.PromptArgument(...). Later Boolean unboxing triggers a NullPointerException: `argumentsMap.put(arg.name(), new MCPPrompt.PromptArgument(arg.name(), arg.description(), arg.required()));` Impact: Any Java agent connecting to a standard MCP server that omits required (or is null) will fail to list prompts, crashing agent initialization. Tools-only MCP servers or any server returning optional arguments without required are affected. Steps to Reproduce Create a Java agent with @MCPSERVER pointing to an MCP server that returns prompts where required is omitted or null. Run the agent. Observe a NullPointerException during MCPServer#listPrompts. <img width="647" height="204" alt="Image" src="https://github.com/user-attachments/assets/0e732225-9020-49fd-9e6b-d62fce680e0d"; /> Caused by: java.lang.NullPointerException: Cannot invoke "java.lang.Boolean.booleanValue()" because the return value of "io.modelcontextprotocol.spec.McpSchema$PromptArgument.required()" is null at org.apache.flink.agents.integrations.mcp.MCPServer.listPrompts(MCPServer.java:354) at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103) ### How to reproduce Create a Java agent with @MCPSERVER pointing to an MCP server that returns prompts where required is omitted or null. Run the agent. Observe a NullPointerException during MCPServer#listPrompts. Expected behavior The agent should treat null required values as false (optional), matching the MCP spec. Agent initialization should succeed, and prompts should be registered correctly. ### Version and environment Flink Agents: 0.2.0 Flink: 2.0.0 Java: 21 OS: macOS (also reproducible on Linux CI) ### Are you willing to submit a PR? - [x] I'm willing to submit a PR! -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
