fix(core): Stringify available tools sent from vercelai (#18197)

[Linear
Ticket](https://linear.app/getsentry/issue/JS-657/available-tools-json-should-be-a-stringified-json-array-of-objects-not)

The available tools sent from our SDKs should generally be in the format
of a stringified array of objects (where an object stores information
about a particular tool). This is true for all AI SDKs except Vercel,
where we send an array of strings. This PR fixes this by parsing the
available tool array and converting the whole array into a proper string
representation.

Author: nicohrubec

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

@@ -197,6 +197,9 @@ describe('Vercel AI integration', () => {
     ]),
   };
 
+  const EXPECTED_AVAILABLE_TOOLS_JSON =
+    '[{"type":"function","name":"getWeather","parameters":{"type":"object","properties":{"location":{"type":"string"}},"required":["location"],"additionalProperties":false,"$schema":"http://json-schema.org/draft-07/schema#"}}]';
+
   const EXPECTED_TRANSACTION_DEFAULT_PII_TRUE = {
     transaction: 'main',
     spans: expect.arrayContaining([
@@ -358,7 +361,7 @@ describe('Vercel AI integration', () => {
           'vercel.ai.prompt.format': expect.any(String),
           'gen_ai.request.messages': expect.any(String),
           'vercel.ai.prompt.toolChoice': expect.any(String),
-          'gen_ai.request.available_tools': expect.any(Array),
+          'gen_ai.request.available_tools': EXPECTED_AVAILABLE_TOOLS_JSON,
           'vercel.ai.response.finishReason': 'tool-calls',
           'vercel.ai.response.id': expect.any(String),
           'vercel.ai.response.model': 'mock-model-id',

dev-packages/node-integration-tests/suites/tracing/vercelai/v5/test.ts

@@ -193,6 +193,9 @@ describe('Vercel AI integration (V5)', () => {
     ]),
   };
 
+  const EXPECTED_AVAILABLE_TOOLS_JSON =
+    '[{"type":"function","name":"getWeather","inputSchema":{"$schema":"http://json-schema.org/draft-07/schema#","type":"object","properties":{"location":{"type":"string"}},"required":["location"],"additionalProperties":false}}]';
+
   const EXPECTED_TRANSACTION_DEFAULT_PII_TRUE = {
     transaction: 'main',
     spans: expect.arrayContaining([
@@ -348,7 +351,7 @@ describe('Vercel AI integration (V5)', () => {
           'vercel.ai.pipeline.name': 'generateText.doGenerate',
           'gen_ai.request.messages': expect.any(String),
           'vercel.ai.prompt.toolChoice': expect.any(String),
-          'gen_ai.request.available_tools': expect.any(Array),
+          'gen_ai.request.available_tools': EXPECTED_AVAILABLE_TOOLS_JSON,
           'vercel.ai.response.finishReason': 'tool-calls',
           'vercel.ai.response.id': expect.any(String),
           'vercel.ai.response.model': 'mock-model-id',

packages/core/src/tracing/vercel-ai/index.ts

@@ -10,7 +10,7 @@ import {
 import { getTruncatedJsonString } from '../ai/utils';
 import { toolCallSpanMap } from './constants';
 import type { TokenSummary } from './types';
-import { accumulateTokensForParent, applyAccumulatedTokens } from './utils';
+import { accumulateTokensForParent, applyAccumulatedTokens, convertAvailableToolsToJsonString } from './utils';
 import type { ProviderMetadata } from './vercel-ai-attributes';
 import {
   AI_MODEL_ID_ATTRIBUTE,
@@ -123,6 +123,13 @@ function processEndedVercelAiSpan(span: SpanJSON): void {
       attributes[GEN_AI_USAGE_OUTPUT_TOKENS_ATTRIBUTE] + attributes[GEN_AI_USAGE_INPUT_TOKENS_ATTRIBUTE];
   }
 
+  // Convert the available tools array to a JSON string
+  if (attributes[AI_PROMPT_TOOLS_ATTRIBUTE] && Array.isArray(attributes[AI_PROMPT_TOOLS_ATTRIBUTE])) {
+    attributes[AI_PROMPT_TOOLS_ATTRIBUTE] = convertAvailableToolsToJsonString(
+      attributes[AI_PROMPT_TOOLS_ATTRIBUTE] as unknown[],
+    );
+  }
+
   // Rename AI SDK attributes to standardized gen_ai attributes
   renameAttributeKey(attributes, AI_PROMPT_MESSAGES_ATTRIBUTE, 'gen_ai.request.messages');
   renameAttributeKey(attributes, AI_RESPONSE_TEXT_ATTRIBUTE, 'gen_ai.response.text');

packages/core/src/tracing/vercel-ai/utils.ts

@@ -70,3 +70,20 @@ export function _INTERNAL_getSpanForToolCallId(toolCallId: string): Span | undef
 export function _INTERNAL_cleanupToolCallSpan(toolCallId: string): void {
   toolCallSpanMap.delete(toolCallId);
 }
+
+/**
+ * Convert an array of tool strings to a JSON string
+ */
+export function convertAvailableToolsToJsonString(tools: unknown[]): string {
+  const toolObjects = tools.map(tool => {
+    if (typeof tool === 'string') {
+      try {
+        return JSON.parse(tool);
+      } catch {
+        return tool;
+      }
+    }
+    return tool;
+  });
+  return JSON.stringify(toolObjects);
+}