Pre-submission Checklist

• I have checked that this question would not be more appropriate as an issue in a specific repository
• I have searched existing discussions and documentation for answers

Question Category

• Protocol Specification
• SDK Usage
• Server Implementation
• General Implementation
• Documentation
• Other

Your Question

I'm using spring-boot-ai to understand how to create an MCP server. I have used the spring-boot-ai-example but they do not seem to work.
I have created a simple "Echo" tool. I do see it registered since I get the schema.

16:40:00.932 [main] INFO c.m.m.a.l.LogAnalyticsMcpServer - >>> Definition: DefaultToolDefinition[name=echo, description=Echoes input, inputSchema={ "$schema" : "https://json-schema.org/draft/2020-12/schema", "type" : "object", "properties" : { "arg0" : { "type" : "string", "description" : "Message to echo" } }, "required" : [ "arg0" ], "additionalProperties" : false }] .... 16:45:33.675 [main] INFO o.s.a.m.s.a.McpServerAutoConfiguration - Enable tools capabilities, notification: true 16:45:33.675 [main] INFO o.s.a.m.s.a.McpServerAutoConfiguration - Registered tools: 3 <--- more than one tool including "echo" are registered 16:45:33.676 [main] INFO o.s.a.m.s.a.McpServerAutoConfiguration - Enable resources capabilities, notification: true 16:45:33.678 [main] INFO o.s.a.m.s.a.McpServerAutoConfiguration - Enable prompts capabilities, notification: true 16:45:33.679 [main] INFO o.s.a.m.s.a.McpServerAutoConfiguration - Enable completions capabilities

Then when I trigger the initialized method, that seems to work ok but when I run tools/call or tools/init nothing happens

{"jsonrpc": "2.0","method":"initialize","params":{"protocolVersion":"2024-11-05","model": "gpt-4","tools": ["echo"],"capabilities": {}}, "id": 1} 16:40:16.138 [pool-5-thread-1] DEBUG i.m.s.t.StdioServerTransportProvider - Received JSON message: {"jsonrpc": "2.0","method":"initialize","params":{"protocolVersion":"2024-11-05","model": "gpt-4","tools": ["echo"],"capabilities": {}}, "id": 1} 16:40:16.138 [pool-5-thread-1] DEBUG i.m.spec.McpSchema - Received JSON message: {"jsonrpc": "2.0","method":"initialize","params":{"protocolVersion":"2024-11-05","model": "gpt-4","tools": ["echo"],"capabilities": {}}, "id": 1} 16:40:16.151 [pool-5-thread-1] DEBUG i.m.spec.McpServerSession - Received request: JSONRPCRequest[jsonrpc=2.0, method=initialize, id=1, params={protocolVersion=2024-11-05, model=gpt-4, tools=[echo], capabilities={}}] 16:40:16.163 [pool-5-thread-1] INFO i.m.server.McpAsyncServer - Client initialize request - Protocol: 2024-11-05, Capabilities: ClientCapabilities[experimental=null, roots=null, sampling=null], Info: null {"jsonrpc":"2.0","id":1,"result":{"protocolVersion":"2024-11-05","capabilities":{"completions":{},"logging":{},"prompts":{"listChanged":true},"resources":{"subscribe":false,"listChanged":true},"tools":{"listChanged":true}},"serverInfo":{"name":"log-analytics-s","version":"1.0.0"},"instructions":"This reactive server provides onprem log anaylitics tools and resources"}} {"jsonrpc": "2.0","method": "tools/call","params": {"name": "echo","arguments": {"arg0": "hello"}},"id": 3} 16:40:57.111 [pool-5-thread-1] DEBUG i.m.s.t.StdioServerTransportProvider - Received JSON message: {"jsonrpc": "2.0","method": "tools/call","params": {"name": "echo","arguments": {"arg0": "hello"}},"id": 3} 16:40:57.112 [pool-5-thread-1] DEBUG i.m.spec.McpSchema - Received JSON message: {"jsonrpc": "2.0","method": "tools/call","params": {"name": "echo","arguments": {"arg0": "hello"}},"id": 3} 16:40:57.112 [pool-5-thread-1] DEBUG i.m.spec.McpServerSession - Received request: JSONRPCRequest[jsonrpc=2.0, method=tools/call, id=3, params={name=echo, arguments={arg0=hello}}]

Then if I change McpServerSession.java handleIncomingRequest and I add "exchangeSink.tryEmitValue" before the flatMap:

if (exchangeSink.tryEmitValue(new McpAsyncServerExchange(this, clientCapabilities.get(), clientInfo.get())).isSuccess()) { logger.debug("Successfully emitted value to exchangeSink"); } else { logger.warn("Failed to emit value to exchangeSink"); } resultMono = this.exchangeSink.asMono().flatMap(exchange -> handler.handle(exchange, request.params()))

Then I do get an answer back. I do not understand what I miss or if something else is wrong or ...
The spring-ai-example code behaves the same ....

{"jsonrpc": "2.0","method":"initialize","params":{"protocolVersion":"2024-11-05","model": "gpt-4","tools": ["echo"],"capabilities": {}}, "id": 1} 16:45:41.224 [pool-5-thread-1] DEBUG i.m.s.t.StdioServerTransportProvider - Received JSON message: {"jsonrpc": "2.0","method":"initialize","params":{"protocolVersion":"2024-11-05","model": "gpt-4","tools": ["echo"],"capabilities": {}}, "id": 1} 16:45:41.225 [pool-5-thread-1] DEBUG i.m.spec.McpSchema - Received JSON message: {"jsonrpc": "2.0","method":"initialize","params":{"protocolVersion":"2024-11-05","model": "gpt-4","tools": ["echo"],"capabilities": {}}, "id": 1} 16:45:41.236 [pool-5-thread-1] DEBUG i.m.spec.McpServerSession - Received request: JSONRPCRequest[jsonrpc=2.0, method=initialize, id=1, params={protocolVersion=2024-11-05, model=gpt-4, tools=[echo], capabilities={}}] 16:45:41.247 [pool-5-thread-1] INFO i.m.server.McpAsyncServer - Client initialize request - Protocol: 2024-11-05, Capabilities: ClientCapabilities[experimental=null, roots=null, sampling=null], Info: null {"jsonrpc":"2.0","id":1,"result":{"protocolVersion":"2024-11-05","capabilities":{"completions":{},"logging":{},"prompts":{"listChanged":true},"resources":{"subscribe":false,"listChanged":true},"tools":{"listChanged":true}},"serverInfo":{"name":"log-analytics-s","version":"1.0.0"},"instructions":"This reactive server provides onprem log anaylitics tools and resources"}} {"jsonrpc": "2.0","method": "tools/call","params": {"name": "echo","arguments": {"arg0": "hello"}},"id": 3} 16:45:52.824 [pool-5-thread-1] DEBUG i.m.s.t.StdioServerTransportProvider - Received JSON message: {"jsonrpc": "2.0","method": "tools/call","params": {"name": "echo","arguments": {"arg0": "hello"}},"id": 3} 16:45:52.825 [pool-5-thread-1] DEBUG i.m.spec.McpSchema - Received JSON message: {"jsonrpc": "2.0","method": "tools/call","params": {"name": "echo","arguments": {"arg0": "hello"}},"id": 3} 16:45:52.825 [pool-5-thread-1] DEBUG i.m.spec.McpServerSession - Received request: JSONRPCRequest[jsonrpc=2.0, method=tools/call, id=3, params={name=echo, arguments={arg0=hello}}] 16:45:52.827 [pool-5-thread-1] DEBUG i.m.spec.McpServerSession - Successfully emitted value to exchangeSink 16:45:52.834 [boundedElastic-1] DEBUG o.s.a.tool.method.MethodToolCallback - Starting execution of tool: echo 16:45:52.836 [boundedElastic-1] INFO c.m.m.ai.loganalytics.test.EchoTool - Echo tool called with message: hello 16:45:52.836 [boundedElastic-1] DEBUG o.s.a.tool.method.MethodToolCallback - Successful execution of tool: echo **16:45:52.836 [boundedElastic-1] DEBUG o.s.a.t.e.DefaultToolCallResultConverter - Converting tool result to JSON. {"jsonrpc":"2.0","id":3,"result":{"content":[{"type":"text","text":"\"hello\""}],"isError":false}}**

Any help is appreciated! Thank you.