Langchain4j and Quarkus AI Services - Not using annotated @Tool to call remote GraphQL API

Question

I have a question about Quarkus Langchain4j.

I have made this Quarkus (Java 25) project with the purpose of exposing an API that receives a search text, processes it with an "extractor” AI service, then talks to an external GraphQL microservice (via a client) to obtain a list of objects, and returns it to the REST API user.

I couldn't get it to work, the calls are made to the AI (Mistral), but they always return an empty body and tools-calling says null, so I gather the tools are not being called. I also tried deleting the ExtractorAiService altogether, so as to have only one @Tool to begin with (you can check the commit history in v2_api branch.

What am I missing? It is my first experience with Quarkus Langchain4j and I've been with this a couple of days to be honest.

REST API - AI service (Quarkus-Langchain4j) https://github.com/wadajo/ai-tourism-madrid

GraphQL API (Quarkus) https://github.com/wadajo/turismo-madrid

Have you tried enabling logging (quarkus.langchain4j.log-requests=true and quarkus.langchain4j.log-responses=true) ? — geoand
– geoand, Commented Nov 24 at 9:33
Yes, thank you, they are enabled. I see the call to api.mistral.ai , and also that’s why I believe the tool is not being called, because the logged response says: - body: {"id":"0f615fb3c06a4d31884553a60e025c44","created":1763978578,"model":"open-mistral-7b","usage":{"prompt_tokens":308,"total_tokens":308,"completion_tokens":0},"object":"chat.completion","choices":[{"index":0,"finish_reason":"stop","message":{"role":"assistant","tool_calls":null,"content":""}}]} — Julio César Estravis
– Julio César Estravis, Commented Nov 24 at 10:04
Any chance you can try your example with some other model (like OpenAI)? — geoand
– geoand, Commented Nov 24 at 11:43
Well, apparently it works, at least it manages to call the remote GraphQL API correctly and the logs show the response. Bad thing is the API response is 500 Error; logs show that I have “insufficient quota” or I exceed some kind of limit. I didn’t know free tier would be so scarce. Anyways, what about Mistral? — Julio César Estravis
– Julio César Estravis, Commented Nov 24 at 20:16

Heiko Rupp · Accepted Answer · 2025-11-27 16:03:03Z

0

Which @Tool annotation are you using? For internal AI agent services you need the one from

dev.langchain4j.agent.tool.Tool;
and not the one from io.quarkiverse.mcp.server

answered 2 days ago

Heiko Rupp

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Julio César Estravis 2 days ago

Yes, Heiko, I am using dev.langchain4j.agent.tool.Tool indeed. Full code is in the Github repo in the main question if you’d like to check it out.

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