> ## Documentation Index > Fetch the complete documentation index at: https://www.bolna.ai/docs/llms.txt > Use this file to discover all available pages before exploring further. # Connect Function Tools and API Integrations > Add built-in function tools and custom API integrations to your Bolna Voice AI agent. Enable calendar booking, call transfers, and connect any external API endpoint. The Tools Tab is where you connect external tools and APIs that your agent's LLM can call during live conversations. This lets your agent take real-time actions like booking appointments, transferring calls, or fetching data from your own backend. Bolna Tools Tab with Function Tools for LLM Models header, Add Tool section showing Calendar Availability, Book Appointment, and Transfer Call cards with Add buttons, and Add a Custom Tool section with Write manually and Generate from cURL options *** ## Built-in Tools Bolna provides ready-to-use tools for common voice agent workflows. Click **+ Add** next to any tool to enable it for your agent. Check open meeting slots from Cal.com in real-time during a call Create calendar bookings directly via Cal.com during the conversation Route the call to a human agent or another phone number Connect any external API endpoint with a custom function schema *** ## Custom Functions For integrations beyond the built-in tools, use **Custom Functions** to connect any API endpoint. You can create a custom function in two ways: Bolna Add a Custom Tool section with Custom Function card showing Write manually button and Generate from cURL button side by side ### Write Manually Click **Write manually** to open a JSON editor where you define the function schema from scratch. This gives you full control over the function name, description, parameters, and API configuration. Bolna custom function configuration modal with a dark code editor showing JSON schema with name test, description, pre_call_message, parameters with startTime and endTime properties, key set to custom_task, and value object with method GET, url, api_token, and headers fields The fields `name`, `description`, `key`, and `method` are mandatory. The `key` must always be set to `"custom_task"`. Do not change this value. ### Generate from cURL Click **Generate from cURL** to paste an existing cURL command. Bolna will parse the request and auto-generate a function schema that you can review and edit before adding it to your agent. Bolna Generate function from cURL modal with a text area containing a sample curl GET request to api.bolna.ai with Authorization Bearer header, Cancel button in red and Generate function button in blue After clicking **Generate function**, Bolna parses the cURL and produces a ready-to-edit function configuration: Bolna generated custom function configuration showing name get_agent, description Called when user asks to get agent details by agent ID, pre_call_message One moment while I fetch the details, parameters object, key custom_task, value with method GET, url https://api.bolna.ai/v2/agent/agent_id, api_token, and headers The cURL import is a starting point. Always review the generated function name, description, and parameters before submitting. See the [Custom Functions guide](/tool-calling/custom-function-calls#generate-from-curl) for a detailed walkthrough. *** ## Managing Added Tools Once you add a tool, it appears as a configurable card in the Tools Tab. | Action | How to do it | | ------------- | ------------------------------------------------------------- | | **Configure** | Click the tool card to edit its parameters and API connection | | **Delete** | Click the delete icon on the tool card to remove it | *** ## Next Steps Full schema reference, examples, and best practices Set up call routing to human agents Configure webhooks and post-call analytics Pass dynamic data into your function tools