diff --git a/bin/chat.js b/bin/chat.js
index bc4e7697..2789f8ee 100644
--- a/bin/chat.js
+++ b/bin/chat.js
@@ -1,6 +1,7 @@
-import http from 'http' // TODO: https
+import { tools } from './tools.js'
 
-const systemPrompt = 'You are a machine learning web application named "hyperparam". ' +
+const systemPrompt =
+  'You are a machine learning web application named "hyperparam". ' +
   'You assist users with building high quality ML models by introspecting on their training set data. ' +
   'The website and api are available at hyperparam.app. ' +
   'Hyperparam uses LLMs to analyze their own training set. ' +
@@ -9,49 +10,124 @@ const systemPrompt = 'You are a machine learning web application named "hyperpar
   'This could be because the data is junk, or because the data requires deeper understanding. ' +
   'This is essential for closing the loop on the ML lifecycle. ' +
   'The quickest way to get started is to upload a dataset and start exploring.'
-const messages = [{ role: 'system', content: systemPrompt }]
+/** @type {Message} */
+const systemMessage = { role: 'system', content: systemPrompt }
+
+const colors = {
+  system: '\x1b[36m', // cyan
+  user: '\x1b[33m', // yellow
+  tool: '\x1b[90m', // gray
+  error: '\x1b[31m', // red
+  normal: '\x1b[0m', // reset
+}
 
 /**
+ * @import { Message } from './types.d.ts'
  * @param {Object} chatInput
- * @returns {Promise<string>}
+ * @returns {Promise<Message>}
  */
-function sendToServer(chatInput) {
-  return new Promise((resolve, reject) => {
-    const json = JSON.stringify(chatInput)
-    const options = {
-      hostname: 'localhost',
-      port: 3000,
-      path: '/api/functions/openai/chat',
-      method: 'POST',
-      headers: {
-        'Content-Type': 'application/json',
-        'Content-Length': json.length,
-      },
-    }
-    const req = http.request(options, res => {
-      let responseBody = ''
-      res.on('data', chunk => {
-        if (chunk[0] !== 123) return // {
-        try {
-          const { content } = JSON.parse(chunk)
-          responseBody += content
+async function sendToServer(chatInput) {
+  const response = await fetch('http://localhost:3000/api/functions/openai/chat', {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify(chatInput),
+  })
+
+  if (!response.ok) {
+    throw new Error(`Request failed: ${response.status}`)
+  }
+
+  // Process the streaming response
+  const streamResponse = { role: 'assistant', content: '' }
+  const reader = response.body.getReader()
+  const decoder = new TextDecoder()
+  let buffer = ''
+
+  while (true) {
+    const { done, value } = await reader.read()
+    if (done) break
+    buffer += decoder.decode(value, { stream: true })
+    const lines = buffer.split('\n')
+    // Keep the last line in the buffer
+    buffer = lines.pop() || ''
+    for (const line of lines) {
+      if (!line.trim()) continue
+      try {
+        const jsonChunk = JSON.parse(line)
+        const { content, error } = jsonChunk
+        if (content) {
+          streamResponse.content += content
           write(content)
-        } catch (error) {
-          reject(error)
+        } else if (error) {
+          console.error(error)
+          throw new Error(error)
+        } else if (jsonChunk.function) {
+          streamResponse.tool_calls ??= []
+          streamResponse.tool_calls.push(jsonChunk)
+        } else if (!jsonChunk.key && jsonChunk.content !== '') {
+          console.log('Unknown chunk', jsonChunk)
         }
-      })
-      res.on('end', () => {
-        if (res.statusCode === 200) {
-          resolve(responseBody)
-        } else {
-          reject(new Error(`request failed: ${res.statusCode}`))
-        }
-      })
-    })
-    req.on('error', reject)
-    req.write(json)
-    req.end()
-  })
+      } catch (err) {
+        console.error('Error parsing chunk', err)
+      }
+    }
+  }
+  return streamResponse
+}
+
+/**
+ * Send messages to the server and handle tool calls.
+ * Will mutate the messages array!
+ *
+ * @import { ToolCall, ToolHandler } from './types.d.ts'
+ * @param {Message[]} messages
+ * @returns {Promise<void>}
+ */
+async function sendMessages(messages) {
+  const chatInput = {
+    messages,
+    tools: tools.map(tool => tool.tool),
+  }
+  const response = await sendToServer(chatInput)
+  messages.push(response)
+  // handle tool results
+  if (response.tool_calls) {
+    /** @type {{ toolCall: ToolCall, tool: ToolHandler, result: Promise<Message> }[]} */
+    const toolResults = []
+    for (const toolCall of response.tool_calls) {
+      const tool = tools.find(tool => tool.tool.function.name === toolCall.function.name)
+      if (tool) {
+        const result = tool.handleToolCall(toolCall)
+        toolResults.push({ toolCall, tool, result })
+      } else {
+        throw new Error(`Unknown tool: ${toolCall.function.name}`)
+      }
+    }
+    write('\n')
+    for (const toolResult of toolResults) {
+      const { toolCall, tool } = toolResult
+      const result = await toolResult.result
+
+      // Construct function call message
+      const args = JSON.parse(toolCall.function?.arguments ?? '{}')
+      const keys = Object.keys(args)
+      let func = toolCall.function.name
+      if (keys.length === 0) {
+        func += '()'
+      } else if (keys.length === 1) {
+        func += `(${args[keys[0]]})`
+      } else {
+        // transform to (arg1 = 111, arg2 = 222)
+        const pairs = keys.map(key => `${key} = ${args[key]}`)
+        func += `(${pairs.join(', ')})`
+      }
+
+      write(colors.tool, `${tool.emoji} ${func}`, colors.normal, '\n\n')
+      messages.push(result)
+    }
+    // send messages with tool results
+    await sendMessages(messages)
+  }
 }
 
 /**
@@ -62,15 +138,10 @@ function write(...args) {
 }
 
 export function chat() {
+  /** @type {Message[]} */
+  const messages = [systemMessage]
   process.stdin.setEncoding('utf-8')
 
-  const colors = {
-    system: '\x1b[36m', // cyan
-    user: '\x1b[33m', // yellow
-    error: '\x1b[31m', // red
-    normal: '\x1b[0m', // reset
-  }
-
   write(colors.system, 'question: ', colors.normal)
 
   process.stdin.on('data', async (/** @type {string} */ input) => {
@@ -81,8 +152,7 @@ export function chat() {
       try {
         write(colors.user, 'answer: ', colors.normal)
         messages.push({ role: 'user', content: input.trim() })
-        const response = await sendToServer({ messages })
-        messages.push({ role: 'assistant', content: response })
+        await sendMessages(messages)
       } catch (error) {
         console.error(colors.error, '\n' + error)
       } finally {
diff --git a/bin/cli.js b/bin/cli.js
index bccbd653..ff0afcd8 100755
--- a/bin/cli.js
+++ b/bin/cli.js
@@ -49,7 +49,7 @@ if (arg === 'chat') {
  */
 function checkForUpdates() {
   const currentVersion = packageJson.version
-  return void fetch('https://registry.npmjs.org/hyperparam/latest')
+  return fetch('https://registry.npmjs.org/hyperparam/latest')
     .then(response => response.json())
     .then(data => {
       const latestVersion = data.version
diff --git a/bin/tools.js b/bin/tools.js
new file mode 100644
index 00000000..8dcd9067
--- /dev/null
+++ b/bin/tools.js
@@ -0,0 +1,77 @@
+import fs from 'fs/promises'
+import { asyncBufferFromFile, parquetQuery, toJson } from 'hyparquet'
+
+/**
+ * @import { Message, ToolCall, ToolHandler } from './types.d.ts'
+ * @type {ToolHandler[]}
+ */
+export const tools = [
+  {
+    emoji: '📂',
+    tool: {
+      type: 'function',
+      function: {
+        name: 'list_files',
+        description: 'List the files in the current directory.',
+        parameters: {
+          type: 'object',
+          properties: {
+            path: { type: 'string', description: 'The path to list files from (optional).' },
+          },
+        },
+      },
+    },
+    /**
+     * @param {ToolCall} toolCall
+     * @returns {Promise<Message>}
+     */
+    async handleToolCall(toolCall) {
+      let { path = '.' } = JSON.parse(toolCall.function.arguments || '{}')
+      if (path.includes('..') || path.includes('~')) {
+        throw new Error('Invalid path: ' + path)
+      }
+      // append to current directory
+      path = process.cwd() + '/' + path
+      // list files in the current directory
+      const filenames = await fs.readdir(path)
+      return { role: 'tool', content: `Files:\n${filenames.join('\n')}`, tool_call_id: toolCall.id }
+    },
+  },
+  {
+    emoji: '📄',
+    tool: {
+      type: 'function',
+      function: {
+        name: 'read_parquet',
+        description: 'Read rows from a parquet file. Do not request more than 5 rows.',
+        parameters: {
+          type: 'object',
+          properties: {
+            filename: { type: 'string', description: 'The name of the parquet file to read.' },
+            rowStart: { type: 'integer', description: 'The start row index.' },
+            rowEnd: { type: 'integer', description: 'The end row index.' },
+            orderBy: { type: 'string', description: 'The column name to sort by.' },
+          },
+          required: ['filename'],
+        },
+      },
+    },
+    /**
+     * @param {ToolCall} toolCall
+     * @returns {Promise<Message>}
+     */
+    async handleToolCall(toolCall) {
+      const { filename, rowStart = 0, rowEnd = 5, orderBy } = JSON.parse(toolCall.function.arguments || '{}')
+      if (rowEnd - rowStart > 5) {
+        throw new Error('Do NOT request more than 5 rows.')
+      }
+      const file = await asyncBufferFromFile(filename)
+      const rows = await parquetQuery({ file, rowStart, rowEnd, orderBy })
+      let content = ''
+      for (let i = rowStart; i < rowEnd; i++) {
+        content += `Row ${i}: ${JSON.stringify(toJson(rows[i]))}\n`
+      }
+      return { role: 'tool', content, tool_call_id: toolCall.id }
+    },
+  },
+]
diff --git a/bin/types.d.ts b/bin/types.d.ts
new file mode 100644
index 00000000..cff9a024
--- /dev/null
+++ b/bin/types.d.ts
@@ -0,0 +1,43 @@
+export interface ToolCall {
+  id: string
+  type: 'function'
+  function: {
+    name: string
+    arguments?: string
+  }
+}
+
+export type Role = 'system' | 'user' | 'assistant' | 'tool'
+
+export interface Message {
+  role: Role
+  content: string
+  tool_calls?: ToolCall[]
+  tool_call_id?: string
+  error?: string
+}
+
+export interface ToolHandler {
+  emoji: string
+  tool: Tool
+  handleToolCall(toolCall: ToolCall): Promise<Message>
+}
+interface ToolProperty {
+  type: string
+  description: string
+}
+
+export interface Tool {
+  type: 'function'
+  function: {
+    name: string
+    description: string
+    parameters?: {
+      type: 'object'
+      properties: Record<string, ToolProperty>
+      required?: string[]
+      additionalProperties?: boolean
+    },
+    strict?: boolean
+  }
+}
diff --git a/package.json b/package.json
index 5a888f74..052cf56f 100644
--- a/package.json
+++ b/package.json
@@ -48,7 +48,7 @@
   },
   "dependencies": {
     "hightable": "0.12.1",
-    "hyparquet": "1.8.7",
+    "hyparquet": "1.9.0",
     "hyparquet-compressors": "1.0.0",
     "react": "18.3.1",
     "react-dom": "18.3.1"
@@ -56,7 +56,7 @@
   "devDependencies": {
     "@eslint/js": "9.22.0",
     "@testing-library/react": "16.2.0",
-    "@types/node": "22.13.9",
+    "@types/node": "22.13.10",
     "@types/react": "19.0.10",
     "@types/react-dom": "19.0.4",
     "@vitejs/plugin-react": "4.3.4",