How to integrate Twelve data MCP with LlamaIndex

This guide walks you through connecting Twelve data to LlamaIndex using the Composio tool router. By the end, you'll have a working Twelve data agent that can list all supported cryptocurrencies today, convert 100 usd to eur right now, show recent dividend payouts for aapl through natural language commands. This guide will help you understand how to give your LlamaIndex agent real control over a Twelve data account through Composio's Twelve data MCP server. Before we dive in, let's take a quick look at the key ideas and tools involved.

Twelve data logoTwelve data
Api Key

Twelve Data is a financial data API providing real-time and historical market data for stocks, forex, crypto, ETFs, and indices. It helps you access accurate, up-to-date financial information for analysis and automation.

97 Tools

Introduction

This guide walks you through connecting Twelve data to LlamaIndex using the Composio tool router. By the end, you'll have a working Twelve data agent that can list all supported cryptocurrencies today, convert 100 usd to eur right now, show recent dividend payouts for aapl through natural language commands.

This guide will help you understand how to give your LlamaIndex agent real control over a Twelve data account through Composio's Twelve data MCP server.

Before we dive in, let's take a quick look at the key ideas and tools involved.

Also integrate Twelve data with

TL;DR

Here's what you'll learn:
  • Set your OpenAI and Composio API keys
  • Install LlamaIndex and Composio packages
  • Create a Composio Tool Router session for Twelve data
  • Connect LlamaIndex to the Twelve data MCP server
  • Build a Twelve data-powered agent using LlamaIndex
  • Interact with Twelve data through natural language

What is LlamaIndex?

LlamaIndex is a data framework for building LLM applications. It provides tools for connecting LLMs to external data sources and services through agents and tools.

Key features include:

  • ReAct Agent: Reasoning and acting pattern for tool-using agents
  • MCP Tools: Native support for Model Context Protocol
  • Context Management: Maintain conversation context across interactions
  • Async Support: Built for async/await patterns

What is the Twelve data MCP server, and what's possible with it?

The Twelve data MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Twelve Data account. It provides structured and secure access to real-time and historical financial market data, so your agent can retrieve stock prices, analyze dividend and earnings history, explore ETFs, and perform currency conversions on your behalf.

  • Comprehensive market data access: Instantly pull up-to-date information on stocks, forex, cryptocurrencies, commodities, and indices to support analysis or decision-making.
  • Dividend and earnings insights: Retrieve detailed dividend payout history and earnings reports, including EPS estimates, actuals, and trend analysis for specific companies.
  • ETF exploration and categorization: Ask your agent to fetch directories of ETFs, sort by assets, family, or market, and explore various ETF types for in-depth portfolio research.
  • Real-time currency conversion: Effortlessly convert amounts between currencies using live exchange rates for accurate financial planning and reporting.
  • Cryptocurrency and commodity discovery: List all supported cryptocurrencies and commodities, helping you quickly identify available assets for further analysis or trading strategies.

What is the Composio tool router, and how does it fit here?

What is Composio SDK?

Composio's Composio SDK helps agents find the right tools for a task at runtime. You can plug in multiple toolkits (like Gmail, HubSpot, and GitHub), and the agent will identify the relevant app and action to complete multi-step workflows. This can reduce token usage and improve the reliability of tool calls. Read more here: Getting started with Composio SDK

The tool router generates a secure MCP URL that your agents can access to perform actions.

How the Composio SDK works

The Composio SDK follows a three-phase workflow:

  1. Discovery: Searches for tools matching your task and returns relevant toolkits with their details.
  2. Authentication: Checks for active connections. If missing, creates an auth config and returns a connection URL via Auth Link.
  3. Execution: Executes the action using the authenticated connection.

Step-by-step Guide

Step by step10 STEPS
1

Prerequisites

Before you begin, make sure you have:
  • Python 3.8/Node 16 or higher installed
  • A Composio account with the API key
  • An OpenAI API key
  • A Twelve data account and project
  • Basic familiarity with async Python/Typescript
2

Getting API Keys for OpenAI, Composio, and Twelve data

OpenAI API key (OPENAI_API_KEY)
  • Go to the OpenAI dashboard
  • Create an API key if you don't have one
  • Assign it to OPENAI_API_KEY in .env
Composio API key and user ID
  • Log into the Composio dashboard
  • Copy your API key from Settings
    • Use this as COMPOSIO_API_KEY
  • Pick a stable user identifier (email or ID)
    • Use this as COMPOSIO_USER_ID
3

Installing dependencies

npm install @composio/llamaindex @llamaindex/openai @llamaindex/tools @llamaindex/workflow dotenv

Create a new Typescript project and install the necessary dependencies:

  • @composio/llamaindex: Composio's LlamaIndex integration
  • @llamaindex/openai: OpenAI LLM integration
  • @llamaindex/tools: MCP client for LlamaIndex
  • @llamaindex/workflow: Workflow framework for LlamaIndex
  • dotenv: Environment variable management
4

Set environment variables

bash
OPENAI_API_KEY=your-openai-api-key
COMPOSIO_API_KEY=your-composio-api-key
COMPOSIO_USER_ID=your-user-id

Create a .env file in your project root:

These credentials will be used to:

  • Authenticate with OpenAI's GPT-5 model
  • Connect to Composio's Tool Router
  • Identify your Composio user session for Twelve data access
5

Import modules

import "dotenv/config";
import readline from "node:readline/promises";
import { stdin as input, stdout as output } from "node:process";

import { Composio } from "@composio/core";

import { mcp } from "@llamaindex/tools";
import { agent as createAgent } from "@llamaindex/workflow";
import { openai } from "@llamaindex/openai";

dotenv.config();

Create a new file called twelve data_llamaindex_agent.ts and import the required modules:

Key imports:

  • dotenv.config loads .env at runtime
  • readline gives us a simple CLI chat loop
  • Composio is the main Composio SDK client
  • mcp connects to an MCP endpoint
  • createAgent builds a LlamaIndex agent
  • openai configures the LLM backend
6

Load environment variables and initialize Composio

const OPENAI_API_KEY = process.env.OPENAI_API_KEY;
const COMPOSIO_API_KEY = process.env.COMPOSIO_API_KEY;
const COMPOSIO_USER_ID = process.env.COMPOSIO_USER_ID;

if (!OPENAI_API_KEY) throw new Error("OPENAI_API_KEY is not set");
if (!COMPOSIO_API_KEY) throw new Error("COMPOSIO_API_KEY is not set");
if (!COMPOSIO_USER_ID) throw new Error("COMPOSIO_USER_ID is not set");

What's happening:

This ensures missing credentials cause early, clear errors before the agent attempts to initialise.

7

Create a Tool Router session and build the agent function

async function buildAgent() {

  console.log(`Initializing Composio client...${COMPOSIO_USER_ID!}...`);
  console.log(`COMPOSIO_USER_ID: ${COMPOSIO_USER_ID!}...`);

  const composio = new Composio({
    apiKey: COMPOSIO_API_KEY,
    provider: new LlamaindexProvider(),
  });

  const session = await composio.create(
    COMPOSIO_USER_ID!,
    {
      toolkits: ["twelve_data"],
    },
  );

  const mcpUrl = session.mcp.url;
  console.log(`Composio Tool Router MCP URL: ${mcpUrl}`);

  const server = mcp({
    url: mcpUrl,
    clientName: "composio_tool_router_with_llamaindex",
    requestInit: {
      headers: {
        "x-api-key": COMPOSIO_API_KEY!,
      },
    },
    // verbose: true,
  });

  const tools = await server.tools();

  const llm = openai({ apiKey: OPENAI_API_KEY, model: "gpt-5" });

  const agent = createAgent({
    name: "composio_tool_router_with_llamaindex",
        description : "An agent that uses Composio Tool Router MCP tools to perform actions.",
    systemPrompt:
      "You are a helpful assistant connected to Composio Tool Router."+
"Use the available tools to answer user queries and perform Twelve data actions." ,
    llm,
    tools,
  });

  return agent;
}

What's happening here:

  • We create a Composio client using your API key and configure it with the LlamaIndex provider
  • We then create a tool router MCP session for your user, specifying the toolkits we want to use (in this case, twelve data)
  • The session returns an MCP HTTP endpoint URL that acts as a gateway to all your configured tools
  • LlamaIndex will connect to this endpoint to dynamically discover and use the available Twelve data tools.
  • The MCP tools are mapped to LlamaIndex-compatible tools and plug them into the Agent.
8

Create an interactive chat loop

async function chatLoop(agent: ReturnType<typeof createAgent>) {
  const rl = readline.createInterface({ input, output });

  console.log("Type 'quit' or 'exit' to stop.");

  while (true) {
    let userInput: string;

    try {
      userInput = (await rl.question("\nYou: ")).trim();
    } catch {
      console.log("\nAgent: Bye!");
      break;
    }

    if (!userInput) {
      continue;
    }

    const lower = userInput.toLowerCase();
    if (lower === "quit" || lower === "exit") {
      console.log("Agent: Bye!");
      break;
    }

    try {
      process.stdout.write("Agent: ");

      const stream = agent.runStream(userInput);
      let finalResult: any = null;

      for await (const event of stream) {
        // The event.data contains the streamed content
        const data: any = event.data;

        // Check for streaming delta content
        if (data?.delta) {
          process.stdout.write(data.delta);
        }

        // Store final result for fallback
        if (data?.result || data?.message) {
          finalResult = data;
        }
      }

      // If no streaming happened, show the final result
      if (finalResult) {
        const answer =
          finalResult.result ??
          finalResult.message?.content ??
          finalResult.message ??
          "";
        if (answer && typeof answer === "string" && !answer.includes("[object")) {
          process.stdout.write(answer);
        }
      }

      console.log(); // New line after streaming completes
    } catch (err: any) {
      console.error("\nAgent error:", err?.message ?? err);
    }
  }

  rl.close();
}

What's happening:

  • We're creating a direct terminal interface to chat with Twelve data
  • The LLM's responses are streamed to the CLI for faster interaction.
  • The agent uses context to maintain conversation history
  • The agent processes the request, selects appropriate Twelve data tools, and returns a result
  • We extract the answer from the result data structure and display it to the user
  • You can type 'quit' or 'exit' to stop the chat loop gracefully
  • Agent responses and any errors are streamed in a clear, readable format
9

Define the main entry point

async function main() {
  try {
    const agent = await buildAgent();
    await chatLoop(agent);
  } catch (err) {
    console.error("Failed to start agent:", err);
    process.exit(1);
  }
}

main();

What's happening here:

  • We're orchestrating the entire application flow
  • The agent gets built with proper error handling
  • Then we kick off the interactive chat loop so you can start talking to Twelve data
10

Run the agent

npx ts-node llamaindex-agent.ts

When prompted, authenticate and authorise your agent with Twelve data, then start asking questions.

Complete Code

Here's the complete code to get you started with Twelve data and LlamaIndex:

import "dotenv/config";
import readline from "node:readline/promises";
import { stdin as input, stdout as output } from "node:process";

import { Composio } from "@composio/core";
import { LlamaindexProvider } from "@composio/llamaindex";

import { mcp } from "@llamaindex/tools";
import { agent as createAgent } from "@llamaindex/workflow";
import { openai } from "@llamaindex/openai";

dotenv.config();

const OPENAI_API_KEY = process.env.OPENAI_API_KEY;
const COMPOSIO_API_KEY = process.env.COMPOSIO_API_KEY;
const COMPOSIO_USER_ID = process.env.COMPOSIO_USER_ID;

if (!OPENAI_API_KEY) {
    throw new Error("OPENAI_API_KEY is not set in the environment");
  }
if (!COMPOSIO_API_KEY) {
    throw new Error("COMPOSIO_API_KEY is not set in the environment");
  }
if (!COMPOSIO_USER_ID) {
    throw new Error("COMPOSIO_USER_ID is not set in the environment");
  }

async function buildAgent() {

  console.log(`Initializing Composio client...${COMPOSIO_USER_ID!}...`);
  console.log(`COMPOSIO_USER_ID: ${COMPOSIO_USER_ID!}...`);

  const composio = new Composio({
    apiKey: COMPOSIO_API_KEY,
    provider: new LlamaindexProvider(),
  });

  const session = await composio.create(
    COMPOSIO_USER_ID!,
    {
      toolkits: ["twelve_data"],
    },
  );

  const mcpUrl = session.mcp.url;
  console.log(`Composio Tool Router MCP URL: ${mcpUrl}`);

  const server = mcp({
    url: mcpUrl,
    clientName: "composio_tool_router_with_llamaindex",
    requestInit: {
      headers: {
        "x-api-key": COMPOSIO_API_KEY!,
      },
    },
    // verbose: true,
  });

  const tools = await server.tools();

  const llm = openai({ apiKey: OPENAI_API_KEY, model: "gpt-5" });

  const agent = createAgent({
    name: "composio_tool_router_with_llamaindex",
    description:
      "An agent that uses Composio Tool Router MCP tools to perform actions.",
    systemPrompt:
      "You are a helpful assistant connected to Composio Tool Router."+
"Use the available tools to answer user queries and perform Twelve data actions." ,
    llm,
    tools,
  });

  return agent;
}

async function chatLoop(agent: ReturnType<typeof createAgent>) {
  const rl = readline.createInterface({ input, output });

  console.log("Type 'quit' or 'exit' to stop.");

  while (true) {
    let userInput: string;

    try {
      userInput = (await rl.question("\nYou: ")).trim();
    } catch {
      console.log("\nAgent: Bye!");
      break;
    }

    if (!userInput) {
      continue;
    }

    const lower = userInput.toLowerCase();
    if (lower === "quit" || lower === "exit") {
      console.log("Agent: Bye!");
      break;
    }

    try {
      process.stdout.write("Agent: ");

      const stream = agent.runStream(userInput);
      let finalResult: any = null;

      for await (const event of stream) {
        // The event.data contains the streamed content
        const data: any = event.data;

        // Check for streaming delta content
        if (data?.delta) {
          process.stdout.write(data.delta);
        }

        // Store final result for fallback
        if (data?.result || data?.message) {
          finalResult = data;
        }
      }

      // If no streaming happened, show the final result
      if (finalResult) {
        const answer =
          finalResult.result ??
          finalResult.message?.content ??
          finalResult.message ??
          "";
        if (answer && typeof answer === "string" && !answer.includes("[object")) {
          process.stdout.write(answer);
        }
      }

      console.log(); // New line after streaming completes
    } catch (err: any) {
      console.error("\nAgent error:", err?.message ?? err);
    }
  }

  rl.close();
}

async function main() {
  try {
    const agent = await buildAgent();
    await chatLoop(agent);
  } catch (err: any) {
    console.error("Failed to start agent:", err?.message ?? err);
    process.exit(1);
  }
}

main();

Conclusion

You've successfully connected Twelve data to LlamaIndex through Composio's Tool Router MCP layer. Key takeaways:
  • Tool Router dynamically exposes Twelve data tools through an MCP endpoint
  • LlamaIndex's ReActAgent handles reasoning and orchestration; Composio handles integrations
  • The agent becomes more capable without increasing prompt size
  • Async Python provides clean, efficient execution of agent workflows
You can easily extend this to other toolkits like Gmail, Notion, Stripe, GitHub, and more by adding them to the toolkits parameter.
TOOLS

Supported Tools

Every Twelve data action and event your agent gets out of the box.

Cash Flow

Tool to get company cash flow statement.

Consolidated Cash Flow

Tool to get raw consolidated cash flow statements.

List Commodities

Tool to retrieve a list of supported commodities.

Correlation Coefficient

Tool to fetch Pearson correlation coefficient between two series over a period.

List Countries

Tool to retrieve a list of countries with ISO codes, names, capitals, and currencies.

Cross Listings

Tool to retrieve cross-listed symbols for a security across multiple exchanges.

List Cryptocurrencies

Tool to list all supported cryptocurrencies.

List Cryptocurrency Exchanges

Tool to list supported cryptocurrency exchanges.

Currency Conversion

Tool to convert an amount from one currency to another.

Dividends

Tool to retrieve dividend payout history for a specified symbol.

Earnings

Tool to retrieve earnings data including EPS estimates and actuals.

EPS Revisions

Tool to provide analysts’ revisions of a company’s future EPS over the last week and month.

EPS Trend

Tool to retrieve EPS trend estimates for a specified company.

ETFS Directory

Tool to fetch a daily updated list of exchange-traded funds sorted by total assets.

ETFS Family

Tool to fetch a comprehensive list of ETFs by family.

Get ETF Types

Tool to retrieve ETF categories by market, including types like 'Equity Precious Metals'.

ETF World

Tool to fetch comprehensive ETF analytics (summary, performance, risk, composition).

ETF World Composition

Tool to fetch global ETF composition details including sector, country, asset allocations, top holdings, and bond metrics.

ETF World Risk

Tool to get global ETF risk metrics.

List supported exchanges

Tool to retrieve a list of supported exchanges.

List supported forex pairs

Tool to retrieve a list of all supported forex currency pairs.

Get AD Indicator

Tool to retrieve Accumulation/Distribution (AD) indicator data for a financial instrument.

Get API Usage

Tool to retrieve your current plan and remaining API credits.

Get APO (Absolute Price Oscillator)

Tool to calculate the Absolute Price Oscillator (APO) for a financial instrument.

Get Aroon Indicator

Tool to retrieve Aroon Indicator data for identifying market trends.

Balance Sheet

Tool to retrieve a company's balance sheet (assets, liabilities, equity).

Balance Sheet Consolidated

Tool to get raw consolidated balance sheet data (assets, liabilities, equity) for a company.

Get Bollinger Bands

Tool to calculate Bollinger Bands (BBANDS) for a financial instrument.

Get Bonds

Tool to retrieve a daily updated list of available bonds (fixed income securities).

Get CCI

Tool to retrieve Commodity Channel Index (CCI) values for a specified security.

Get Ceiling (CEIL)

Tool to retrieve the Ceiling (CEIL) transformation for a time series.

Get Chande Momentum Oscillator

Tool to retrieve Chande Momentum Oscillator (CMO) data for a security.

Get Detrended Price Oscillator

Tool to calculate the Detrended Price Oscillator (DPO) for a specified financial instrument.

Get Earliest Timestamp

Tool to return the first available timestamp for a symbol and interval.

Get End of Day Price

Tool to retrieve end of day (EOD) closing price and metadata for a financial instrument.

Global ETF Performance

Tool to get global ETF performance metrics (trailing and annual returns).

Get exchange schedule

Tool to get trading sessions and hours for exchanges.

Get Fund Holders

Tool to retrieve mutual fund holders for a company.

Get Funds

Tool to fetch a daily updated list of available investment funds.

Get Heikin Ashi Candles

Tool to retrieve Heikin Ashi candlestick data that smooths price action by averaging values.

Get HLC3 Average

Tool to calculate the High, Low, Close Average (HLC3) for a security over a specified period.

Get Hilbert Transform Sine Wave

Tool to fetch Hilbert Transform Sine Wave (HT_SINE) data for an instrument.

Get Ichimoku Cloud Indicator

Tool to retrieve Ichimoku Kinko Hyo indicator data for analyzing trend direction, support/resistance levels, and trading opportunities.

Income Statement

Tool to retrieve a company's income statement data (annual or quarterly).

Insider Transactions

REQUIRES PRO, ULTRA, OR ENTERPRISE PLAN.

Get Available Intervals

Tool to retrieve a list of available time intervals supported by the API.

Get Keltner Channel

Tool to retrieve Keltner Channel indicator data for volatility-based technical analysis.

Key Executives

REQUIRES ULTRA OR ENTERPRISE PLAN.

Get Last Change

Tool to retrieve the latest update timestamps for a fundamentals dataset.

Get Linear Regression Angle

Tool to calculate the linear regression angle for a given time series of stock prices.

Get Linear Regression Intercept

Tool to calculate the y-intercept of a linear regression line for a given dataset.

Get Linear Regression Slope

Tool to calculate the linear regression slope for a given dataset over a specified period.

Get Base-10 Logarithm (LOG10)

Tool to compute the base-10 logarithm (LOG10) of a specified input value.

Get Logo

Tool to retrieve official logo URLs for a symbol.

Get MACD

Tool to calculate the Moving Average Convergence Divergence (MACD) for a specified financial instrument.

Get MAMA

Tool to fetch MESA Adaptive Moving Average (MAMA) indicator data.

Market Movers

Tool to retrieve a snapshot of top gainers or losers for a specified market.

Get Market State

Tool to report current open/closed status for exchanges.

Get Maximum Value

Tool to calculate and return the highest value within a specified data series over a given period.

Get McGinley Dynamic Indicator

Tool to calculate the McGinley Dynamic indicator, which provides a refined moving average that adapts to market volatility.

Get Median Price

Tool to calculate and retrieve the Median Price (MEDPRICE) technical indicator for a security.

Get Minus Directional Indicator

Tool to calculate and return the Minus Directional Indicator (MINUS_DI) for a security.

Global Mutual Fund Performance

Tool to get global mutual fund performance metrics (trailing, annual, quarterly, load-adjusted returns).

Mutual Funds World Risk

Tool to fetch global mutual fund risk metrics.

Global Mutual Fund Summary

Tool to retrieve a global mutual fund summary snapshot.

Global Mutual Fund Sustainability

Tool to get global mutual fund sustainability and ESG metrics.

Get Plus Directional Indicator

Tool to fetch the Plus Directional Indicator (PLUS_DI) time series data for a security.

Get Price

Tool to retrieve the latest market price for a specified financial instrument.

Price Target

Tool to fetch analysts' price target dataset for equities.

Get Profile

Tool to retrieve company profile.

Recommendations

Retrieve aggregated analyst recommendations for a stock.

Get Rate of Change (ROC)

Tool to retrieve Rate of Change (ROC) indicator data for a security.

Get ROCP (Rate of Change Percentage)

Tool to calculate and return the Rate of Change Percentage (ROCP) for a financial security.

Get ROCR100

Tool to calculate the Rate of Change Ratio 100 (ROCR100) for a security.

Get Relative Volume

Tool to fetch relative volume (RVOL) data for a security.

Stock Splits

Tool to retrieve historical stock split events.

Splits Calendar

Tool to retrieve a calendar of stock split events.

Get Statistics

Tool to retrieve key company statistics including valuation and financial overview.

Get Stochastic RSI

Tool to calculate the Stochastic Relative Strength Index (Stochastic RSI) for a specified financial instrument.

Get Summation (SUM)

Tool to calculate the cumulative total (Summation) of a specified data series over a defined time period.

Get Technical Indicators List

Tool to retrieve a comprehensive list of available technical indicators.

Get TEMA (Triple Exponential Moving Average)

Tool to calculate the Triple Exponential Moving Average (TEMA) for a financial instrument.

Get Variance (VAR)

Tool to calculate the statistical variance of a financial data series.

Get Weighted Close Price

Tool to calculate and retrieve the Weighted Close Price (WCLPRICE) for a security.

Get Weighted Moving Average (WMA)

Tool to calculate and retrieve the Weighted Moving Average (WMA) for a security over a specified period.

List market indices

Tool to retrieve a list of market indices.

Institutional Holders

Tool to retrieve institutional holders positions for a company.

Mutual Funds Family

Tool to list all available mutual fund families.

Mutual Funds List

Tool to retrieve a daily updated list of mutual funds sorted by total assets.

Mutual Funds World Composition

Tool to fetch global mutual fund portfolio composition including sectors, asset allocation, top holdings, and bond metrics.

Options Chain

Tool to retrieve the options chain for a given symbol and optional expiration date.

Options Expiration

Tool to retrieve available option expiration dates.

Quote

Tool to retrieve the latest market data for a specified symbol.

List Stocks

Tool to retrieve a list of stocks.

Symbol Search

Tool to search for financial instruments by symbol or company name.

Technical Indicators

Tool to fetch time-series data for a specific technical indicator.

Time Series

Tool to retrieve historical and real-time time series data for a specified symbol.

FAQ

Frequently asked questions

With a standalone Twelve data MCP server, the agents and LLMs can only access a fixed set of Twelve data tools tied to that server. However, with the Composio Tool Router, agents can dynamically load tools from Twelve data and many other apps based on the task at hand, all through a single MCP endpoint.

Yes, you can. LlamaIndex fully supports MCP integration. You get structured tool calling, message history handling, and model orchestration while Tool Router takes care of discovering and serving the right Twelve data tools.

Yes, absolutely. You can configure which Twelve data scopes and actions are allowed when connecting your account to Composio. You can also bring your own OAuth credentials or API configuration so you keep full control over what the agent can do.

All sensitive data such as tokens, keys, and configuration is fully encrypted at rest and in transit. Composio is SOC 2 Type 2 compliant and follows strict security practices so your Twelve data data and credentials are handled as safely as possible.

Start with Twelve data.It takes 30 seconds.

Managed auth, hosted MCP servers, and every Twelve data tool your agent needs.Free to start.

Start building