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Gemini 2.5 Pro and Gemini 3 Pro API Integration Guide

Complete guide to integrating Google's Gemini 2.5 Pro, Gemini 2.5 Flash, and Gemini 3 Pro models via API. Includes native format and OpenAI-compatible examples.

Crazyrouter Team

January 22, 2026 / 1109 views

Gemini 2.5 Pro and Gemini 3 Pro API Integration Guide

Crazyrouter

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Google's Gemini models offer exceptional multimodal capabilities, advanced reasoning, and competitive pricing. This guide covers how to integrate Gemini 2.5 Pro, Gemini 2.5 Flash, and the latest Gemini 3 Pro through Crazyrouter's API.

Supported Gemini Models#

Model	Input ($/1M)	Output ($/1M)	Best For
gemini-3-pro-preview	$1.25	$7.50	Latest generation
gemini-3-pro-preview-thinking	$1.25	$7.50	Extended reasoning
gemini-3-pro-image-preview	$1.25	$7.50	Image generation
gemini-3-flash-preview	$0.15	$0.60	Fast responses
gemini-2.5-pro	$1.25	$10.00	Long documents
gemini-2.5-pro-thinking	$1.25	$10.00	Complex reasoning
gemini-2.5-flash	$0.30	$2.50	Production workloads
gemini-2.5-flash-lite	$0.10	$0.40	Cost-effective
gemini-2.5-flash-image	$0.30	$2.50	Image generation

Quick Start with OpenAI-Compatible API#

The easiest way to use Gemini models is through the OpenAI-compatible endpoint:

python

from openai import OpenAI

client = OpenAI(
    api_key="sk-your-api-key",
    base_url="https://ai.crazyrouter.us/v1",
    default_headers={
        "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36"
    }
)

response = client.chat.completions.create(
    model="gemini-2.5-pro",
    messages=[
        {"role": "user", "content": "Explain the theory of relativity in simple terms."}
    ]
)

print(response.choices[0].message.content)

Native Gemini API Format#

For advanced features, use the native Gemini API format:

Text Generation#

bash

curl -X POST "https://ai.crazyrouter.us/v1beta/models/gemini-2.5-pro:generateContent" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer sk-your-api-key" \
  -H "User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36" \
  -d '{
    "contents": [{
      "parts": [{"text": "Write a poem about artificial intelligence."}]
    }]
  }'

Streaming Text Generation#

bash

curl -X POST "https://ai.crazyrouter.us/v1beta/models/gemini-3-pro-preview:streamGenerateContent" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer sk-your-api-key" \
  -H "User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36" \
  -d '{
    "contents": [{
      "parts": [{"text": "Explain quantum computing step by step."}]
    }]
  }'

Extended Thinking with Gemini#

Gemini models support extended thinking for complex reasoning:

python

# Gemini 2.5 Pro with thinking
response = client.chat.completions.create(
    model="gemini-2.5-pro-thinking",
    messages=[
        {"role": "user", "content": "Solve this complex math problem step by step: Find all prime numbers p such that p^2 + 2 is also prime."}
    ]
)

# Gemini 3 Pro with thinking
response = client.chat.completions.create(
    model="gemini-3-pro-preview-thinking",
    messages=[
        {"role": "user", "content": "Analyze this algorithm's time complexity."}
    ]
)

Image Generation with Gemini#

Gemini 2.5 Flash Image#

bash

curl -X POST "https://ai.crazyrouter.us/v1beta/models/gemini-2.5-flash-image:generateContent" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer sk-your-api-key" \
  -H "User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36" \
  -d '{
    "contents": [{
      "parts": [{"text": "Generate an image of a futuristic city at sunset"}]
    }],
    "generationConfig": {
      "responseModalities": ["image", "text"]
    }
  }'

Gemini 3 Pro Image (with aspect ratio control)#

bash

curl -X POST "https://ai.crazyrouter.us/v1beta/models/gemini-3-pro-image-preview:generateContent" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer sk-your-api-key" \
  -H "User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36" \
  -d '{
    "contents": [{
      "parts": [{"text": "A serene Japanese garden with cherry blossoms"}]
    }],
    "generationConfig": {
      "responseModalities": ["image"],
      "aspectRatio": "16:9"
    }
  }'

Google Search Integration#

Gemini models can access real-time information via Google Search:

bash

curl -X POST "https://ai.crazyrouter.us/v1beta/models/gemini-2.5-flash:generateContent" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer sk-your-api-key" \
  -H "User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36" \
  -d '{
    "contents": [{
      "parts": [{"text": "What are the latest developments in AI as of today?"}]
    }],
    "tools": [{
      "googleSearch": {}
    }]
  }'

Flash Lite Models (Cost-Effective)#

For high-volume, cost-sensitive applications:

python

# Standard Flash Lite
response = client.chat.completions.create(
    model="gemini-2.5-flash-lite",
    messages=[{"role": "user", "content": "Summarize this text briefly."}]
)

# Flash Lite with thinking
response = client.chat.completions.create(
    model="gemini-2.5-flash-lite-thinking",
    messages=[{"role": "user", "content": "Solve this logic puzzle."}]
)

Python SDK Example#

python

from openai import OpenAI

client = OpenAI(
    api_key="sk-your-api-key",
    base_url="https://ai.crazyrouter.us/v1",
    default_headers={
        "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36"
    }
)

# Gemini 3 Pro for complex reasoning
response = client.chat.completions.create(
    model="gemini-3-pro-preview",
    messages=[
        {"role": "system", "content": "You are a helpful AI assistant with expertise in science."},
        {"role": "user", "content": "Explain CRISPR gene editing and its potential applications."}
    ],
    temperature=0.7,
    max_tokens=2000
)

print(response.choices[0].message.content)

Pricing Comparison#

Model	Input ($/1M)	Output ($/1M)
gemini-3-pro-preview	$1.25	$7.50
gemini-2.5-pro	$1.25	$10.00
gemini-2.5-flash	$0.30	$2.50
gemini-2.5-flash-lite	$0.10	$0.40
gemini-flash-latest	$0.30	$2.50

Pricing Disclaimer: The prices shown in this article are for demonstration purposes only and may change at any time. Actual billing will be based on the real-time prices displayed when you make your request.

Best Practices#

Use Flash for production: Gemini 2.5 Flash offers excellent performance at lower cost
Enable thinking for complex tasks: Use thinking-enabled models for math and reasoning
Leverage multimodal capabilities: Gemini excels at image and video understanding
Use streaming for long responses: Better user experience with real-time output

Model Selection Guide#

Use Case	Recommended Model
General chat	gemini-2.5-flash
Complex reasoning	gemini-2.5-pro-thinking or gemini-3-pro-preview-thinking
Image generation	gemini-2.5-flash-image or gemini-3-pro-image-preview
Cost-sensitive	gemini-2.5-flash-lite
Latest features	gemini-3-pro-preview