Build a Reddit Research Agent with Claude and MCP

import { Anthropic } from "@anthropic-ai/sdk";
import { Client } from "@modelcontextprotocol/sdk/client/index.js";
import { StdioClientTransport } from "@modelcontextprotocol/sdk/client/stdio.js";

// 1. Initialize the Anthropic SDK client
const anthropic = new Anthropic({
  apiKey: process.env.ANTHROPIC_API_KEY,
});

async function runRedditResearchAgent(researchGoal: string) {
  // 2. Connect to SubScraper MCP Server via StdioClientTransport
  const transport = new StdioClientTransport({
    command: "npx",
    args: ["-y", "@subscraper/mcp"],
    env: {
      ...process.env,
      SUBSCRAPER_API_KEY: process.env.SUBSCRAPER_API_KEY || "",
    },
  });

  const mcpClient = new Client(
    { name: "reddit-research-worker", version: "1.0.0" },
    { capabilities: {} }
  );

  await mcpClient.connect(transport);
  console.log("✓ Connected to SubScraper MCP Server");

  // 3. Inspect and convert MCP tools to Anthropic tool schema
  const { tools: mcpTools } = await mcpClient.listTools();
  const anthropicTools: Anthropic.Tool[] = mcpTools.map((tool) => ({
    name: tool.name,
    description: tool.description || "",
    input_schema: tool.inputSchema as Anthropic.Tool.InputSchema,
  }));

  const messages: Anthropic.MessageParam[] = [
    {
      role: "user",
      content: researchGoal,
    },
  ];

  console.log(`Starting research loop: "${researchGoal}"\n`);

  // 4. Autonomous tool execution loop
  let isSearching = true;
  let iterations = 0;
  const MAX_ITERATIONS = 8;

  while (isSearching && iterations < MAX_ITERATIONS) {
    iterations++;
    console.log(`[Turn ${iterations}] Prompting Claude...`);

    const response = await anthropic.messages.create({
      model: "claude-3-7-sonnet-20250219",
      max_tokens: 4096,
      system:
        "You are an autonomous Reddit research agent. Use the provided tools to search discussions, fetch nested comment trees, and synthesize evidence-backed qualitative briefs with verbatim quotes and permalinks.",
      tools: anthropicTools,
      messages,
    });

    if (response.stop_reason === "tool_use") {
      // Append assistant message containing tool calls
      messages.push({
        role: "assistant",
        content: response.content,
      });

      const toolResults: Anthropic.ToolResultBlockParam[] = [];

      // Execute each tool call through the MCP client
      for (const block of response.content) {
        if (block.type === "tool_use") {
          console.log(`  ↳ Executing: ${block.name}(${JSON.stringify(block.input)})`);

          try {
            const result = await mcpClient.callTool({
              name: block.name,
              arguments: block.input as Record<string, unknown>,
            });

            const textOutput =
              result.content && Array.isArray(result.content)
                ? result.content.map((c) => (c.type === "text" ? c.text : "")).join("\n")
                : JSON.stringify(result);

            toolResults.push({
              type: "tool_result",
              tool_use_id: block.id,
              content: textOutput,
            });
          } catch (err) {
            console.error(`Failed to execute ${block.name}:`, err);
            toolResults.push({
              type: "tool_result",
              tool_use_id: block.id,
              content: `Error: ${err instanceof Error ? err.message : String(err)}`,
              is_error: true,
            });
          }
        }
      }

      // Return tool results back to Claude
      messages.push({
        role: "user",
        content: toolResults,
      });
    } else {
      // Agent finished autonomous research
      isSearching = false;
      const finalReport = response.content
        .filter((c) => c.type === "text")
        .map((c) => (c as { text: string }).text)
        .join("\n");

      console.log("\n================ RESEARCH SYNTHESIS ================\n");
      console.log(finalReport);
      return finalReport;
    }
  }

  await transport.close();
}

// Example usage
runRedditResearchAgent(
  "Search r/SaaS for complaints about Stripe pricing and alternatives. Highlight top 3 recurring friction points with quotes."
);