LangChain Agent + vLLM Qwen2-VL + @tool

### Checked other resources - [x] This is a bug, not a usage question. - [x] I added a clear and descriptive title that summarizes this issue. - [x] I used the GitHub search to find a similar question and didn't find it. - [x] I am sure that this is a bug in LangChain rather than my code. - [x] The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package). - [x] This is not related to the langchain-community package. - [x] I posted a self-contained, minimal, reproducible example. A maintainer can copy it and run it AS IS. ### Package (Required) - [x] langchain - [x] langchain-openai - [ ] langchain-anthropic - [ ] langchain-classic - [ ] langchain-core - [ ] langchain-model-profiles - [ ] langchain-tests - [ ] langchain-text-splitters - [ ] langchain-chroma - [ ] langchain-deepseek - [ ] langchain-exa - [ ] langchain-fireworks - [ ] langchain-groq - [ ] langchain-huggingface - [ ] langchain-mistralai - [ ] langchain-nomic - [ ] langchain-ollama - [ ] langchain-openrouter - [ ] langchain-perplexity - [ ] langchain-qdrant - [ ] langchain-xai - [ ] Other / not sure / general ### Related Issues / PRs _No response_ ### Reproduction Steps / Example Code (Python) ```python # from dataclasses import dataclass # from langchain.agents import create_agent # from langchain.chat_models import init_chat_model # from langchain.tools import tool, ToolRuntime # from langgraph.checkpoint.memory import InMemorySaver # from langchain.agents.structured_output import ToolStrategy # from langchain_openai import ChatOpenAI # # Define system prompt # SYSTEM_PROMPT = """You are an expert weather forecaster, who speaks in puns. # You have access to two tools: # - get_weather_for_location: use this to get the weather for a specific location # - get_user_location: use this to get the user's location # If a user asks you for the weather, make sure you know the location. If you can tell from the question that they mean wherever they are, use t…