Function handleChatTool

server/src/mcp/chat-tool.ts:185–247

(
  args: Record<string, unknown>,
  authContext?: MCPAuthContext,
)

 * Handle the chat_with_addie tool call
 */
export async function handleChatTool(
  args: Record<string, unknown>,
  authContext?: MCPAuthContext,
): Promise<string> {
  const message = args.message;
  const history = args.history as ConversationMessage[] | undefined;

  if (!message || typeof message !== 'string') {
    return JSON.stringify({
      error: 'message is required and must be a string',
    });
  }

  // Check if knowledge search is ready
  if (!isKnowledgeReady()) {
    return JSON.stringify({
      error: 'Addie is still initializing. Please try again in a moment.',
    });
  }

  try {
    const client = getChatClient();

    // Convert history to thread context format expected by AddieClaudeClient
    const threadContext = history?.map((msg) => ({
      user: msg.role === 'user' ? 'user' : 'assistant',
      text: msg.content,
    }));

    // Cost cap (#2790 / #2950): bucket by the authenticated MCP sub
    // when available. In prod, MCP auth is OAuth Bearer, so `sub` is
    // the user or M2M client id — either is a legitimate per-caller
    // bucket key. The anonymous tier (~$1/day) is the right ceiling
    // for safe-tools-only chat traffic. If auth is disabled (dev
    // mode) or the sub is missing, fall back to `uncapped: true` so
    // local testing isn't budget-limited; prod MCP requires auth by
    // default so the fallback doesn't expose a production surface.
    const sub = authContext?.sub;
    const costOption = sub && sub !== 'anonymous'
      ? { costScope: { userId: `mcp:${sub}`, tier: 'anonymous' as const } }
      : { uncapped: true as const };

    const response = await client.processMessage(
      message,
      threadContext,
      undefined, // No request-specific tools for anonymous
      undefined, // No rules override
      { maxIterations: 5, ...costOption }, // Lower iteration limit for anonymous users
    );

    const result: ChatResponse = {
      response: response.text,
      tools_used: response.tools_used,
    };

    return JSON.stringify(result);
  } catch (error) {
    logger.error({ error }, 'MCP Chat: Error processing message');