本文通过简单数学计算，示例llama_index使用agent解决复杂任务过程。

假设mac本地llama_index环境已安装，过程参考

mac测试ollama llamaindex-CSDN博客

测试mac笔记本内存8G，所以使用较小LLM完成示例。

ollama pull qwen3:1.7b

qwen3:1.7b能力较弱，需要prompt明确要求使用agent工具，遵守计算前后顺序。

prompt示例如下

"使用agent工具计算，遵守计算的先后顺序， 20 + (2 x 3) * 4?"

程序示例如下

from llama_index.core.agent import ReActAgent
from llama_index.core.tools import FunctionTool
from llama_index.core import Settings
from llama_index.llms.ollama import OllamaSettings.embed_model = OllamaEmbedding(model_name="yxl/m3e:latest")  
Settings.llm = Ollama(model="qwen3:1.7b", request_timeout=360) # 定义数学计算工具
def multiply(a: float, b: float) -> float:"""Multiply two numbers and returns the product"""return a * bmultiply_tool = FunctionTool.from_defaults(fn=multiply)def add(a: float, b: float) -> float:"""Add two numbers and returns the sum"""return a + badd_tool = FunctionTool.from_defaults(fn=add)# 实例化 ReActAgent
agent = ReActAgent.from_tools([multiply_tool, add_tool], verbose=True
)# 测试代理
response = agent.chat("使用agent工具计算，遵守计算的先后顺序， 20 + (2 x 3) * 4?")
print(response)

如下所示，llama_index将示例式子计算过程分解为agent工具的调用过程。

首先是红色部分，调用multiply完成2*3=6。

然后是棕色部分，调用multiply完成6*4=24。

最后是紫色部分，调用add完成20+24=44。

> Running step 91dcc552-f7b2-4cc3-9af1-cf07812cc8b8. Step input: 请使用agent工具计算，遵守计算的先后顺序， 20 + (2 x 3) * 4?
Thought: <think>
Okay, let's see. The user wants to calculate 20 + (2 x 3) * 4 using the agent tool. Hmm, first I need to break down the expression according to the order of operations. Parentheses come first, so I should calculate 2 x 3 first. That's 6. Then multiply by 4, which gives 24. Now add that to 20. So 20 + 24 equals 44. Wait, but the tools available are multiply and add. Let me check the tools again. The multiply tool takes two numbers, and the add tool adds two numbers. So I need to do the multiplication first. Let me do the steps: first multiply 2 and 3, then multiply the result by 4, then add 20. So the steps would be: multiply 2 and 3 to get 6, then multiply by 4 to get 24, then add 20. So the final answer should be 44. I need to use the tools in the correct order. Let me use the multiply tool first for 2 and 3, then multiply the result by 4, then add 20. Let's see how that works.
</think>

Thought: I need to calculate 20 + (2 x 3) * 4 using the available tools. First, multiply 2 and 3, then multiply the result by 4, and finally add 20.
Action: multiply
Action Input: {"a": 2, "b": 3}
Observation: 6

Thought: Now multiply the result (6) by 4.
Action: multiply
Action Input: {"a": 6, "b": 4}
Observation: 24

Thought: Add 24 to 20.
Action: add
Action Input: {'a': 24, 'b': 20}
Observation: 44
> Running step ab11a064-bdde-42df-9fcf-3aa409e18eab. Step input: None
Thought: I can answer without using any more tools. I'll use the user's language to answer
Answer: 44
44