feat(langchain): add X402SearchTool for API discovery

packages/langchain/src/tools.ts

@@ -114,4 +114,6 @@ export class DataAnalysisTool extends X402Tool {
       apiUrl: 'http://localhost:3001/api/analyze',
     });
   }
-}
+}
+
+export { X402SearchTool } from './tools/x402search';

packages/langchain/src/tools/x402search.ts

@@ -0,0 +1,92 @@
+import { StructuredTool } from '@langchain/core/tools';
+import { z } from 'zod';
+import { X402AgentClient, AgentPaymentConfig } from '@xpaysh/agent-kit-core';
+
+const X402SEARCH_URL = 'https://x402search.xyz/v1/search';
+const X402SEARCH_CHAIN_ID = 8453; // Base mainnet — required for x402search payments
+
+export type X402SearchToolConfig = Omit<AgentPaymentConfig, 'chainId'> & {
+  limit?: number;
+};
+
+const X402SearchSchema = z.object({
+  query: z.string().describe('Natural language search query, e.g. "btc price" or "NFT metadata"'),
+});
+
+export class X402SearchTool extends StructuredTool {
+  name = 'search_apis';
+  description = `Search for API services and data providers by natural language capability query.
+Searches 14,000+ indexed APIs across crypto, DeFi, NFT, weather, finance, AI, and more.
+Returns matching services with endpoints and payment metadata.
+Cost: $0.01 USDC per query via x402 protocol on Base mainnet — paid automatically.
+
+Coinbase Bazaar lists services. x402search searches them by capability — complementary, not competing.
+
+Examples:
+- search_apis("token price") -> price feeds including CoinGecko, try402.fun
+- search_apis("crypto market data") -> CoinGecko, Heyanon, analytics APIs
+- search_apis("NFT metadata") -> NFT-related APIs
+- search_apis("btc price") -> targeted BTC price feeds`;
+
+  schema = X402SearchSchema;
+
+  private client: X402AgentClient;
+  private limit: number;
+
+  constructor(config: X402SearchToolConfig) {
+    super();
+    this.limit = config.limit ?? 5;
+    this.client = new X402AgentClient({
+      ...config,
+      chainId: X402SEARCH_CHAIN_ID,
+    });
+  }
+
+  async _call(input: z.infer<typeof X402SearchSchema>): Promise<string> {
+    const url = `${X402SEARCH_URL}?q=${encodeURIComponent(input.query)}&limit=${this.limit}`;
+
+    try {
+      const response = await this.client.makePayedCall({ url, method: 'GET' });
+      const data = response.data;
+      const results = Array.isArray(data) ? data : (data?.results ?? []);
+
+      if (!results.length) {
+        return JSON.stringify({
+          success: true,
+          query: input.query,
+          results: [],
+          message: `No APIs found for '${input.query}'. Try broader terms: 'crypto' or 'token price'.`,
+        });
+      }
+
+      const formatted = results.slice(0, this.limit).map((r: any) => ({
+        url: r.resource_url,
+        rank: r.rank,
+        accepts: (r.accepts ?? []).map((a: any) => ({
+          network: a.network,
+          max_amount: a.max_amount,
+          payTo: a.payTo,
+        })),
+      }));
+
+      return JSON.stringify({
+        success: true,
+        query: input.query,
+        count: formatted.length,
+        payment: { cost: response.cost, currency: response.currency, hash: response.paymentHash },
+        results: formatted,
+      }, null, 2);
+
+    } catch (error: any) {
+      return JSON.stringify({
+        success: false,
+        error: `x402search request failed: ${error.message}`,
+        hint: 'Ensure the wallet has USDC on Base mainnet (eip155:8453).',
+      });
+    }
+  }
+
+  getSpendingStats() {
+    return this.client.getSpendingStats();
+  }
+}