> ## 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. # Prompting Guide and Best Practices for Bolna Voice AI > Write effective prompts for Bolna Voice AI agents. Use variables, prompt modules, and best practices to build high-performing conversational agents. This guide covers how to write effective prompts, use variables and prompt modules, and optimize your agent for performance. *** ## Variables Variables let you inject dynamic data into your prompts. There are two types: Defined by you. Passed via the API at call time or from CSV rows during [batch calling](/batch-calling). Examples: `{customer_name}`, `{order_id}`, `{city}`. Predefined by Bolna. Available automatically in every call. Examples: `agent_id`, `call_sid`. ### Using Variables in the Prompt Editor Type `{` in the prompt editor to open the variable dropdown. It shows both **User Variables** and **System Variables**. Agent Prompt editor with curly brace dropdown open showing User Variables section with referrer_name, referee_name, city, user_number and System Variables section with agent_id, call_sid With `{`, you can: * **Select** an existing user or system variable * **Define a new variable** by typing a name that does not exist yet (e.g., `{appointment_date}`) ### Testing Variables Any variable you define with `{variable_name}` in your prompt **automatically appears** as an editable input field in the testing section below the prompt. Fill in test values to preview how the prompt behaves before going live. Prompt variables for testing section showing Asia Kolkata UTC plus 05 30 timezone selector and auto-detected variable fields for referrer_name, referee_name, city, and user_number User variables are passed via the API at call time or from CSV rows during [batch calling](/batch-calling). System variables like `agent_id` and `call_sid` are filled automatically by Bolna. *** ## Using @ to Insert Modules, Functions, and Variables Type `@` in the prompt editor to open a dropdown that lets you select and insert: * **Prompt Modules** - pre-built prompt blocks for common tasks * **Custom Functions** - functions defined in the [Tools Tab](/agent-setup/tools-tab) * **Variables** - existing variables already used in your prompt Agent Prompt editor with at-sign dropdown open showing Prompt Modules list including Email Collection, Number Collection, Name Collection, Persuasion, and Variables Reference With `@`, you can only **select** existing items. You cannot create new variables, functions, or modules. To create a new variable, use `{variable_name}` instead. ## Prompt Modules Prompt modules are pre-built prompt blocks that handle common tasks like email collection, persuasion, objection handling, and more. Insert a module and customize it instead of writing from scratch. ### Browse Modules Click the **Browse Modules** button in the top-right of the Agent Prompt section to open the full modules library. Browse by category, read what each module does, and insert it into your prompt with one click. Browse Modules panel with left sidebar showing categories Collection, Optional, and Flow, and right panel showing Email Collection module with description, full prompt text, and Insert into editor button Each module shows: * **What Prompt Does** - a short description of the module's purpose * **Prompt** - the full prompt text that will be inserted * **Insert into editor** - click to add it to your current prompt Modules panel showing Interview Reminder module with categories Collection, Optional, Flow, Sector, Universal on the left, and prompt content with call flow instructions on the right ### Available Module Categories | Category | What it contains | | -------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | | **Collection** | Email Collection, Number Collection, Name Collection | | **Optional** | Persuasion, Variables Reference, Pricing and Plans, Objection Handling, Knowledge Base, Hang Up Prompt, Handover and Escalation, FAQ Block, Extraction Schema, Eligibility Criteria, Compliance Healthcare, Compliance Finance, Closing Branches | | **Flow** | Outbound Survey, Outbound Lead, Inbound Verification | | **Sector** | Industry-specific modules | | **Universal** | General-purpose modules that work across use cases | Modules are a great starting point. Insert one, then customize the prompt text to fit your specific use case and tone. *** ## Writing Effective Prompts Begin with a clear, concise prompt. Add details incrementally as you test and refine. Start with: "You will not speak more than 2 sentences at a time." This keeps responses fast and natural. | Section | Purpose | Example | | ---------------- | --------------- | ------------------------------------------- | | **Personality** | Tone and feel | "warm, perceptive, and results-driven" | | **Context** | Role background | "You are calling on behalf of Acme Corp..." | | **Instructions** | Tasks and flow | "Ask for their order number first..." | | **Guardrails** | Restrictions | "Never discuss competitor products..." | Prompt engineering takes iteration. If your agent does not follow instructions as expected, refine the prompt step by step rather than rewriting everything at once. *** ## Choosing the Right Agent Type Natural conversations from a plain-English prompt. Creative and flexible, but requires fine-tuning and costs more. Full control over exact sentences. Cheaper with no hallucination risk, but conversations are limited to the defined tree. | | Free Flowing | IVR | | ---------------------- | -------------- | ------------------------- | | **Setup** | Write a prompt | Build a conversation tree | | **Flexibility** | High | Low | | **Hallucination risk** | Possible | None | | **Cost** | Higher | Lower | Start with an [agent template](/agents-library) and customize it. Templates are built to run on default settings. *** ## Optimizing for Performance For low-latency, high-quality conversations: | Component | Recommended | | --------------- | ---------------------------- | | **LLM** | Azure / gpt-4.1-mini cluster | | **Voice** | ElevenLabs | | **Transcriber** | Deepgram | | **Telephony** | Plivo | Make sure the voice you choose supports the language you have configured. Use the [Playground](/agent-setup/agent-tab) to test your agent thoroughly before making live calls. Telephone calling burns credits quickly. *** ## Next Steps Configure prompts, languages, and advanced settings Start from a pre-built template Pass dynamic data into calls with context variables Writing prompts in native scripts