fix(core): Flatten gen_ai.request.available_tools in google-genai (#18194)

While investigating [this
ticket](https://linear.app/getsentry/issue/JS-657/available-tools-json-should-be-a-stringified-json-array-of-objects-not)
I noticed that available tools are sent as a nested instead of a flat
array in google genai, which seems like a bug to me.

The format I would expect and how we do it in other integrations is:
[{tool-definition}, {tool-definition}]

What we actually send atm is:
[[{tool-definition}], [{tool-definition}]]

This PR fixes this to instead send a flat list of tool definitions.

Author: nicohrubec

dev-packages/node-integration-tests/suites/tracing/google-genai/test.ts

@@ -204,6 +204,9 @@ describe('Google GenAI integration', () => {
     });
   });
 
+  const EXPECTED_AVAILABLE_TOOLS_JSON =
+    '[{"name":"controlLight","parametersJsonSchema":{"type":"object","properties":{"brightness":{"type":"number"},"colorTemperature":{"type":"string"}},"required":["brightness","colorTemperature"]}}]';
+
   const EXPECTED_TRANSACTION_TOOLS = {
     transaction: 'main',
     spans: expect.arrayContaining([
@@ -215,7 +218,7 @@ describe('Google GenAI integration', () => {
           'sentry.origin': 'auto.ai.google_genai',
           'gen_ai.system': 'google_genai',
           'gen_ai.request.model': 'gemini-2.0-flash-001',
-          'gen_ai.request.available_tools': expect.any(String), // Should include tools
+          'gen_ai.request.available_tools': EXPECTED_AVAILABLE_TOOLS_JSON,
           'gen_ai.request.messages': expect.any(String), // Should include contents
           'gen_ai.response.text': expect.any(String), // Should include response text
           'gen_ai.response.tool_calls': expect.any(String), // Should include tool calls
@@ -236,7 +239,7 @@ describe('Google GenAI integration', () => {
           'sentry.origin': 'auto.ai.google_genai',
           'gen_ai.system': 'google_genai',
           'gen_ai.request.model': 'gemini-2.0-flash-001',
-          'gen_ai.request.available_tools': expect.any(String), // Should include tools
+          'gen_ai.request.available_tools': EXPECTED_AVAILABLE_TOOLS_JSON,
           'gen_ai.request.messages': expect.any(String), // Should include contents
           'gen_ai.response.streaming': true,
           'gen_ai.response.text': expect.any(String), // Should include response text

packages/core/src/tracing/google-genai/index.ts

@@ -115,7 +115,7 @@ function extractRequestAttributes(
 
       // Extract available tools from config
       if ('tools' in config && Array.isArray(config.tools)) {
-        const functionDeclarations = config.tools.map(
+        const functionDeclarations = config.tools.flatMap(
           (tool: { functionDeclarations: unknown[] }) => tool.functionDeclarations,
         );
         attributes[GEN_AI_REQUEST_AVAILABLE_TOOLS_ATTRIBUTE] = JSON.stringify(functionDeclarations);