> ## Documentation Index > Fetch the complete documentation index at: https://www.voiceflow.com/docs/llms.txt > Use this file to discover all available pages before exploring further. # Tools > Definitions for tools, with explanations of how each term fits into Voiceflow and links to the related documentation. ## Tools ### Tool Something a playbook can call mid-conversation: functions, API tools, MCP tools, integrations, and the built-in system tools. Each also has a step form for use at a fixed point in a workflow. **Also asked as:** - things the assistant can do besides talking - let the agent take an action in another system - what can the agent actually do besides chat - actions the assistant can take in other systems **Related:** [Agent tools](/docs/resources/glossary/build/agent-setup#agent-tools) · [System tools](#system-tools) **Documented in:** [Agent tools](/docs/documentation/build/tools/overview) ### Function Custom JavaScript that runs in Voiceflow's sandbox and returns through a named path. Code runs remotely in an isolated sandbox; it communicates back only through its return value (`outputVars`, `next`, `trace`) and can make HTTP requests with `fetch`. **Also asked as:** - write custom code the agent can run - a JavaScript tool that calls an external API - return different outcomes from my own code **Related:** [Function step](/docs/resources/glossary/build/steps#function-step) · [Function path](#function-path) · [Function variable](#function-variable) · [Code step](/docs/resources/glossary/build/steps#code-step) **Documented in:** [Function tool › Creating a Function tool](/docs/documentation/build/tools/function-tool#creating-a-function-tool) · [Function tool › How function code works](/docs/documentation/build/tools/function-tool#how-function-code-works) · [Function tool › Making API requests with fetch](/docs/documentation/build/tools/function-tool#making-api-requests-with-fetch) ### Function tool A function exposed to a playbook as something it can call. The agent calls it on its own when the conversation requires it; in a workflow the same function runs through a Function step. **Also asked as:** - let the assistant run my custom code when it needs to - expose a function to a skill - give a playbook access to my JavaScript - custom logic the agent can invoke **Related:** [Function](#function) · [Function step](/docs/resources/glossary/build/steps#function-step) **Documented in:** [Function tool › Using the Function tool](/docs/documentation/build/tools/function-tool#using-the-function-tool) · [Function tool › In a playbook](/docs/documentation/build/tools/function-tool#in-a-playbook) ### Function path One of the named exits a function can return through. Paths are what let a function branch rather than just return a value. They apply in Function steps only, not inside a playbook. **Also asked as:** - make my function send the flow one way or another - success and failure exits from custom code - multiple outcomes from one function - route the workflow based on my code's result **Related:** [Function](#function) · [Function step](/docs/resources/glossary/build/steps#function-step) **Documented in:** [Function tool › next: choosing a path](/docs/documentation/build/tools/function-tool#next-choosing-a-path) ### Function variable An input or output a function declares. Inputs are passed in when it runs (`args.inputVars`); outputs are written back for later steps to read (`outputVars`). **Also asked as:** - pass a value into my code and get one back - read the function's result in a later step - declare inputs and outputs for my function - what a function receives and returns **Related:** [Function](#function) · [Variable](/docs/resources/glossary/knowledge-and-data#variable) **Documented in:** [Function tool › Accessing input variables](/docs/documentation/build/tools/function-tool#accessing-input-variables) · [Function tool › outputVars: setting variables](/docs/documentation/build/tools/function-tool#outputvars-setting-variables) ### API tool A saved HTTP request an agent can make, tested from the editor and used in a playbook (the agent decides when) or a workflow (the API step, at a fixed point). **Also asked as:** - call a REST endpoint from the assistant - make an HTTP request to our own backend - connect the bot to an API that has no prebuilt connector **Related:** [API step](/docs/resources/glossary/build/steps#api-step) · [API tool variable](#api-tool-variable) · [Asynchronous tool call](#asynchronous-tool-call) · [Secret](/docs/resources/glossary/knowledge-and-data#secret) **Documented in:** [API tool › Creating an API tool](/docs/documentation/build/tools/api-tool#creating-an-api-tool) · [API tool › Testing the API tool](/docs/documentation/build/tools/api-tool#testing-the-api-tool) · [API tool › Using the API tool](/docs/documentation/build/tools/api-tool#using-the-api-tool) ### API tool variable An input an API tool substitutes into its request, so one saved request can serve many calls. **Also asked as:** - put a variable into the request URL or body - parameterise a saved request - a placeholder in the request that changes per call - dynamic values in an API request **Related:** [API tool](#api-tool) **Documented in:** [API tool › Creating an API tool](/docs/documentation/build/tools/api-tool#creating-an-api-tool) ### Asynchronous tool call Running an API or Function tool in the background so the conversation continues immediately: fire and forget when the response is not needed, deferred response when it still matters. The async toggle is set per instance, not per tool. **Also asked as:** - don't make the visitor wait for a slow request - run a call in the background and carry on talking - log something without holding up the reply **Related:** [API tool](#api-tool) · [Function](#function) **Documented in:** [API tool › Running API tools asynchronously](/docs/documentation/build/tools/api-tool#running-api-tools-asynchronously) · [Function tool › Running Function tools asynchronously](/docs/documentation/build/tools/function-tool#running-function-tools-asynchronously) ### Integration Calls a third-party service such as Salesforce, Shopify or Zendesk through a prebuilt connector: Airtable, Gmail, Google Sheets, HubSpot, Make, Salesforce, Shopify, Twilio and Zendesk each expose a set of actions. **Also asked as:** - connect our CRM or helpdesk to the assistant - a prebuilt connector to a third-party app - send an email or create a ticket from the bot **Related:** [Integration step](/docs/resources/glossary/build/steps#integration-step) · [Tool](#tool) **Documented in:** [Agent tools › Available integrations](/docs/documentation/build/tools/overview#available-integrations) · [Agent tools › Setting up an integration](/docs/documentation/build/tools/overview#setting-up-an-integration) · [Airtable tool](/docs/documentation/build/tools/airtable-tool) · [Gmail tool](/docs/documentation/build/tools/gmail-tool) · [Google Sheets tool](/docs/documentation/build/tools/google-sheets-tool) · [HubSpot tool](/docs/documentation/build/tools/hubspot-tool) · [Make tool](/docs/documentation/build/tools/make-tool) · [Salesforce tool](/docs/documentation/build/tools/salesforce-tool) · [Twilio tool](/docs/documentation/build/tools/twilio-tool) · [Zendesk tool](/docs/documentation/build/tools/zendesk-tool) ### System tools Native capabilities built into Voiceflow that need no setup: knowledge base search, web search, buttons, cards, carousels, skip turn, end and call forward. Enabled by a toggle at the agent level (then available in every playbook) or per playbook, where a local override can change a tool's settings and trigger. **Also asked as:** - the built-in tools the assistant comes with - switch on web search or buttons for the agent - change a built-in tool's behaviour in one playbook only **Related:** [Knowledge base tool](#knowledge-base-tool) · [Buttons tool](#buttons-tool) · [Web search](#web-search) · [Skip turn](#skip-turn) · [End tool](#end-tool) **Documented in:** [System tools › Enabling system tools](/docs/documentation/build/tools/system-tools#enabling-system-tools) · [System tools › Local overrides](/docs/documentation/build/tools/system-tools#local-overrides) ### Knowledge base tool The system tool that searches the knowledge base to answer a question. Configurable: the trigger, a custom query, query re-writing, the chunk limit (1–10, default 3), metadata filtering, tool messages, and source URLs in the reply. **Also asked as:** - make the assistant answer from our uploaded documents - control how many passages the bot pulls per question - show where an answer came from **Related:** [Knowledge base](/docs/resources/glossary/knowledge-and-data#knowledge-base) · [Chunk](/docs/resources/glossary/ai-terms#chunk) · [Metadata](/docs/resources/glossary/knowledge-and-data#metadata) **Documented in:** [System tools › Knowledge base](/docs/documentation/build/tools/system-tools#knowledge-base) · [Querying the knowledge base › Configuring the knowledge base tool](/docs/documentation/build/querying-the-knowledge-base#configuring-the-knowledge-base-tool) ### Buttons tool The system tool that lets the agent generate clickable options in its replies, so users choose rather than type. **Also asked as:** - let the AI offer quick-reply choices on its own - generated buttons in an agentic reply - the assistant suggests options to tap - AI-generated choice buttons **Related:** [Buttons step](/docs/resources/glossary/build/steps#buttons-step) · [System tools](#system-tools) **Documented in:** [System tools › Buttons](/docs/documentation/build/tools/system-tools#buttons) ### Cards tool The system tool that lets the agent build rich cards — title, description, image, action buttons — from the conversation context. **Also asked as:** - the assistant shows a product tile it composed itself - dynamic cards rather than a fixed Card step - let the agent show a rich card with an image and buttons - cards generated during the conversation **Related:** [Card step](/docs/resources/glossary/build/steps#card-step) · [Carousels tool](#carousels-tool) **Documented in:** [System tools › Cards](/docs/documentation/build/tools/system-tools#cards) ### Carousels tool The system tool that lets the agent show several cards in a horizontally scrollable carousel when it needs to present multiple options at once. **Also asked as:** - the bot lists several items to swipe through - generated carousel of results - the agent shows several products to scroll through - a swipeable set of options in an agentic reply **Related:** [Carousel step](/docs/resources/glossary/build/steps#carousel-step) · [Cards tool](#cards-tool) **Documented in:** [System tools › Carousels](/docs/documentation/build/tools/system-tools#carousels) ### Web search A system tool that lets the agent search the web for current information during a conversation. **Also asked as:** - search the internet when the answer isn't in our content - give the bot live web results - up-to-date information from outside the knowledge base - let the assistant look something up on the web - answer with current information from the internet - browse for facts the knowledge base doesn't have **Related:** [Knowledge base tool](#knowledge-base-tool) · [System tools](#system-tools) **Documented in:** [System tools › Web search](/docs/documentation/build/tools/system-tools#web-search) ### Skip turn A system tool that lets the agent stay quiet and wait for the user instead of replying — when someone says "hold on" or "give me a second". **Also asked as:** - the bot should wait silently when told to hold on - don't reply until the person is ready - pause without sending a message **Related:** [System tools](#system-tools) · [Global no-reply](/docs/resources/glossary/build/behaviour#global-no-reply) **Documented in:** [System tools › Skip turn](/docs/documentation/build/tools/system-tools#skip-turn) ### Call forward tool The system tool that forwards the active call to a phone number or SIP address when the agent decides to. Voice projects only. **Also asked as:** - let the assistant transfer the call when it judges it necessary - agentic transfer to a human line - transfer the call to a person when the agent decides - agentic call transfer to a SIP address **Related:** [Call forward step](/docs/resources/glossary/build/steps#call-forward-step) **Documented in:** [System tools › Call forward](/docs/documentation/build/tools/system-tools#call-forward) ### End tool A system tool that lets the agent end the conversation when it judges it complete. **Also asked as:** - let the assistant close the chat itself - the bot decides the conversation is over - the agent ends the call on its own - let the bot wrap up the conversation when done **Related:** [End step](/docs/resources/glossary/build/steps#end-step) **Documented in:** [System tools › End](/docs/documentation/build/tools/system-tools#end) ### HubSpot tool Connects an agent to HubSpot actions through the configured integration. **Documented in:** [HubSpot tool](/docs/documentation/build/tools/hubspot-tool)