When Google Gemini decides to use one of Metorial's integrations, it returns function calls that you need to handle. This guide shows you how.

How Function Calling Works

1. You send a prompt to Gemini with Metorial tools available
2. If Gemini needs to use an integration, it returns function calls instead of text
3. You execute those function calls through Metorial
4. You can send the results back to Gemini for further processing

Basic Function Call Handling

Here's how to detect and handle function calls:

await metorial.withProviderSession(
  metorialGoogle,
  { serverDeployments: ['your-server-deployment-id'] },
  async session => {
    let response = await genAI.models.generateContent({
      model: 'gemini-1.5-pro-latest',
      contents: [{
        role: 'user',
        parts: [{ 
          text: 'Search for the metorial/websocket-explorer repository on GitHub' 
        }]
      }],
      config: {
        tools: session.tools
      }
    });

    // Check if Gemini wants to call functions
    let functionCalls = response.candidates?.[0]?.content?.parts
      ?.filter(part => part.functionCall)
      .map(part => part.functionCall!);

    if (functionCalls && functionCalls.length > 0) {
      // Execute the function calls through Metorial
      let toolResponses = await session.callTools(functionCalls);
      console.log('Tool responses:', toolResponses);
    } else {
      // No function calls, just regular text response
      let text = response.candidates?.[0]?.content?.parts?.[0]?.text;
      console.log(text);
    }
  }
);

Complete Example with Error Handling

await metorial.withProviderSession(
  metorialGoogle,
  { serverDeployments: ['your-server-deployment-id'] },
  async session => {
    try {
      let response = await genAI.models.generateContent({
        model: 'gemini-1.5-pro-latest',
        contents: [{
          role: 'user',
          parts: [{ text: 'Find my next meeting on the calendar' }]
        }],
        config: {
          tools: session.tools
        }
      });

      let functionCalls = response.candidates?.[0]?.content?.parts
        ?.filter(part => part.functionCall)
        .map(part => part.functionCall!);

      if (functionCalls && functionCalls.length > 0) {
        let toolResponses = await session.callTools(functionCalls);
        
        // Use the tool responses as needed
        toolResponses.forEach(response => {
          console.log('Tool result:', response);
        });
      }
    } catch (error) {
      console.error('Error:', error);
    }
  }
);

What Happens Behind the Scenes

When you call session.callTools(functionCalls):

1. Metorial validates the function calls
2. Executes them against the appropriate integrations
3. Returns the results in a format Gemini can understand

Metorial handles all the complexity of authentication, API calls, and error handling automatically.