Raw HTTP Tool Loop

Same loop, no SDK

The agentic tool loop from Track 5 works identically with raw HTTP. The wire format is exactly what the SDK was building for you. Useful when you're embedded in a constrained environment, debugging a wire-level issue, or implementing the loop in a language without a Gemini SDK.

The shape on the wire

Tool declarations go in the tools field of the request body. The model's response contains functionCall parts; you respond in the next user turn with functionResponse parts. Same as SDK, just spelled out.

Code

Raw HTTP tool loop — ~50 lines·python

import httpx, json

API_KEY = '...'  # from env
MODEL   = 'gemini-2.5-flash'
BASE    = f'https://generativelanguage.googleapis.com/v1beta/models/{MODEL}'

TOOLS = [{
    'functionDeclarations': [{
        'name': 'get_weather',
        'description': 'Get current weather for a location.',
        'parameters': {
            'type': 'object',
            'properties': {
                'location': {'type': 'string', 'description': 'City name'},
            },
            'required': ['location'],
        },
    }]
}]

def execute(name, args):
    if name == 'get_weather':
        # Pretend we called a real weather API
        return {'temperature_c': 22, 'conditions': 'clear', 'location': args['location']}
    return {'error': f'Unknown tool: {name}'}

def run_tool_loop(prompt: str, max_iter: int = 10) -> str:
    contents = [{'role': 'user', 'parts': [{'text': prompt}]}]
    headers = {'x-goog-api-key': API_KEY, 'Content-Type': 'application/json'}

    with httpx.Client(timeout=60) as client:
        for _ in range(max_iter):
            resp = client.post(
                f'{BASE}:generateContent',
                headers=headers,
                json={'contents': contents, 'tools': TOOLS},
            )
            resp.raise_for_status()
            data = resp.json()
            model_content = data['candidates'][0]['content']
            parts = model_content.get('parts', [])
            calls = [p['functionCall'] for p in parts if 'functionCall' in p]

            if not calls:
                return ''.join(p.get('text', '') for p in parts)

            # Append model's call turn
            contents.append(model_content)

            # Execute and build user turn
            fn_parts = []
            for fc in calls:
                result = execute(fc['name'], fc.get('args', {}))
                fn_parts.append({
                    'functionResponse': {
                        'name':     fc['name'],
                        'id':       fc.get('id', ''),
                        'response': {'result': result},
                    },
                })
            contents.append({'role': 'user', 'parts': fn_parts})

    raise RuntimeError(f'Loop exhausted after {max_iter} iterations')

print(run_tool_loop('What's the weather in Seoul?'))

Same idea via OAuth — wrap the body in 'request'·python

# OAuth version: prepend project, wrap original body in {model, project, request}
def run_tool_loop_oauth(prompt, max_iter=10):
    token   = get_access_token()
    project = load_code_assist(token)
    contents = [{'role': 'user', 'parts': [{'text': prompt}]}]
    headers = {
        'Authorization': f'Bearer {token}',
        'Content-Type':  'application/json',
    }

    with httpx.Client(timeout=60) as client:
        for _ in range(max_iter):
            resp = client.post(
                'https://cloudcode-pa.googleapis.com/v1internal:generateContent',
                headers=headers,
                json={
                    'model':   'gemini-2.5-flash',
                    'project': project,
                    'request': {'contents': contents, 'tools': TOOLS},
                },
            )
            data = resp.json()['response']
            model_content = data['candidates'][0]['content']
            parts = model_content.get('parts', [])
            calls = [p['functionCall'] for p in parts if 'functionCall' in p]

            if not calls:
                return ''.join(p.get('text', '') for p in parts)
            # ... same loop as API key path

Exercise

Take the raw HTTP loop from the first code block and add a second tool: convert_temperature(value: number, from_unit: string, to_unit: string). Ask Flash: "What's the weather in Seoul, and convert that temperature to Fahrenheit?" Confirm the model chains both tools, and that your response correctly uses functionResponse in user turns.

Same loop, no SDK

The shape on the wire

Code

External links

Exercise

Progress

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