Getting jsonrpc exception: Unable to parse the JSON message: io.vertx.core.json.DecodeException: Failed to decode:No content to map due to end-of-input

[muralidharz]

Getting the following error when trying out the weather stdio sample project:

2025-05-08 09:30:29,133 ERROR [io.qua.mcp.ser.std.run.StdioMcpMessageHandler] (pool-8-thread-1) Unable to parse the JSON message: io.vertx.core.json.DecodeException: Failed to decode:No content to map due to end-of-input
at [Source: REDACTED (StreamReadFeature.INCLUDE_SOURCE_IN_LOCATION disabled); line: 1]
at io.quarkus.vertx.runtime.jackson.QuarkusJacksonJsonCodec.fromParser(QuarkusJacksonJsonCodec.java:148)
at io.quarkus.vertx.runtime.jackson.QuarkusJacksonJsonCodec.fromString(QuarkusJacksonJsonCodec.java:115)
at io.vertx.core.json.JsonObject.fromJson(JsonObject.java:1262)
at io.vertx.core.json.JsonObject.(JsonObject.java:51)
at io.quarkiverse.mcp.server.stdio.runtime.StdioMcpMessageHandler$1.run(StdioMcpMessageHandler.java:85)
at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:539)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
at java.base/java.lang.Thread.run(Thread.java:840)
Caused by: com.fasterxml.jackson.databind.exc.MismatchedInputException: No content to map due to end-of-input
at [Source: REDACTED (StreamReadFeature.INCLUDE_SOURCE_IN_LOCATION disabled); line: 1]
at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:59)
at com.fasterxml.jackson.databind.ObjectMapper._initForReading(ObjectMapper.java:5008)
at com.fasterxml.jackson.databind.ObjectMapper._readValue(ObjectMapper.java:4885)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3036)
at io.quarkus.vertx.runtime.jackson.QuarkusJacksonJsonCodec.fromParser(QuarkusJacksonJsonCodec.java:145)
... 9 more

{"jsonrpc":"2.0","id":null,"error":{"code":-32700,"message":"Unable to parse the JSON message"}}
2025-05-08 09:31:00,086 INFO [io.quarkus] (Shutdown thread) weather stopped in 0.014s

[mkouba]

Hello, how do you run the app? What's the MCP client?

CC @maxandersen

[muralidharz]

I tried all: jbang, Claude desktop, map inspector and all. I don't think the issue is on the client side. Even when the service is coming up, these errors are showing up on quarkus logs.

[maxandersen]

@muralidharz understood but can you show the actual command you are running/ configuring with ?