fix: GeminiModel argument in README

[tosi29]

Description

Fix README about GeminiModel argument

Related Issues

N/A

Documentation PR

N/A

Type of Change

Documentation update

Testing

How have you tested the change? Verify that the changes do not break functionality or introduce warnings in consuming repositories: agents-docs, agents-tools, agents-cli

• I ran hatch run prepare

The result has no difference between before/after this change.

For Reference

NG: It doesn't work with error.

import os
from strands import Agent
from strands.models.gemini import GeminiModel

gemini_model = GeminiModel(
    api_key=os.environ["MY_API_KEY"],
    model_id="gemini-2.5-flash",
    params={"temperature": 0.7}
)

agent = Agent(model=gemini_model)
agent("Tell me about Agentic AI")

OK: It works.

import os
from strands import Agent
from strands.models.gemini import GeminiModel

gemini_model = GeminiModel(
    client_args={
        "api_key": os.environ["MY_API_KEY"],
    },
    model_id="gemini-2.5-flash",
    params={"temperature": 0.7}
)

agent = Agent(model=gemini_model)
agent("Tell me about Agentic AI")

Checklist

• I have read the CONTRIBUTING document
• I have added any necessary tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• My changes generate no new warnings
• Any dependent changes have been merged and published

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