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Custom Mid-Call Tools let your AI assistant interact with external systems during calls. Whether checking inventory, verifying customer data, or fetching real-time information, these tools make your AI more powerful and connected.

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Overview

Custom Mid-Call Tools enable your AI assistant to:
  • Make real-time API calls during conversations
  • Fetch or submit data to your systems
  • Make informed decisions based on live data
  • Provide accurate, up-to-date information to callers

Key Benefits

  • No coding required - just configure the API endpoint and parameters - AI automatically knows when and how to use the tools - Real-time data access during calls - Seamless integration with your existing systems
Mid-call tools and MCP servers both live under the Mid call tools / MCP page in the sidebar. Use a mid-call tool for a single HTTP endpoint you define by hand, and an MCP server to connect a remote server that exposes many tools at once.

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Tool types

When you create a tool you choose one of two types:

HTTP request

Call your own API directly. You set the URL, method, headers, parameters and (optionally) a static body. Best when you already have an endpoint.

Automation Platform

Autocalls creates a linked flow for you in the Automation Platform. The tool’s endpoint is generated and locked automatically — you just build the logic in the flow and end with a Return Response step. Best for no-code, multi-step logic.

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Setting Up Your Tool

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1. Basic Configuration

Main Tool Configuration
1

Access Tool Creation

Navigate to Mid call tools and click Create Mid-Call Tool
2

Configure Main Settings

Fill in the essential details:
  • Name: Letters, numbers and underscores, starting with a letter or underscore (up to 64 characters, e.g., check_order_status)
  • Description: Explain when and how the AI should use this tool
  • Endpoint: Your API URL (e.g., https://api.yourcompany.com/orders)
  • Timeout: How long to wait for responses (1–30 seconds)
  • Method: Choose GET, POST, PUT, PATCH, or DELETE
  • Body format: For write methods (POST/PUT/PATCH), send the body as JSON (default) or form-encoded (application/x-www-form-urlencoded)
3

Add Headers

Common headers you might need:
Content-Type: application/json
Authorization: Bearer your_token

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2. Variable Configuration

Variable Configuration
1

Define Parameters

These are the pieces of information your AI will collect during the call:
Name: order_number
Type: string
Description: "10-digit order number from the customer"
2

Set Validation Rules

Add format requirements in the description:
"Date in dd/mm/yyyy format"
"Phone number without spaces"
"Email address for confirmation"

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Understanding Parameter Types

String

Text values like names, addresses, or reference numbers
Type: string
Examples: "John Doe", "123 Main St"

Number

Whole numbers like quantities or IDs
Type: number
Examples: 42, 1500

Float

Decimal numbers like prices or amounts
Type: float
Examples: 19.99, 4.5

Boolean

True/false values for yes/no situations
Type: boolean
Examples: true, false
Each parameter can be marked required or optional. Optional parameters are only sent when the AI actually collected a value, so your endpoint won’t receive empty fields. Add format hints in the description (e.g. "Date in dd/mm/yyyy", "Phone without spaces").

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Static fields

Static fields are fixed key/value pairs that are always sent with every request — the AI never changes them. Use them for constants like a tenant id, a channel, or a source tag. 
source: autocalls
tenant: acme
channel: sms
Static field values also support system variables (e.g. set caller to {{customer_phone}}).

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System variables & dynamic values

There are two ways to inject dynamic data into your tool:

AI-extracted parameters

Wrapped in single braces {param}. Replaced with the value the AI collected during the conversation. Used in the URL path/query.
https://api.example.com/orders/{order_id}

System & account variables

Wrapped in double braces {{variable}}. Filled in automatically by the platform at call time. Usable in the URL, header values, and static field values.
Authorization: Bearer {{crm_key}}
These system variables are injected automatically — no setup needed:
VariableValue
{{customer_phone}}The other party’s phone number (caller for inbound, callee for outbound). Empty on web/chat.
{{assistant_phone}}The assistant’s own phone number, if it has one.
{{assistant_id}}The assistant’s unique ID.
{{assistant_name}}The assistant’s name.
{{current_date}}Current date in the assistant’s timezone (e.g. 2026-06-15).
{{current_time}}Current time in the assistant’s timezone (e.g. 14:30).
Any custom account variables you define are also available as {{name}} and can be used the same way.

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Dynamic Endpoints

When using variables in your endpoint URL, make sure to enclose them in curly braces and use the exact parameter name.
You can make your endpoints dynamic using variables: 
Basic URL:
https://api.example.com/orders/status

With Variables:
https://api.example.com/orders/{order_id}/status
The AI will automatically replace {order_id} with the actual value collected during the conversation.

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Testing Made Easy

Automatic Testing

Click Test tool to fire a real request with realistic sample data:
  • String parameters: "Sample data"
  • Number parameters: 42
  • Float parameters: 19.99
  • Boolean parameters: true
  • System variables like {{customer_phone}} are filled with realistic placeholders (e.g. +1234567890, the assistant name/id)
You’ll see the request data, response code and body, helping you verify everything works before going live.
Automation Platform tools don’t have a Test tool button — you test them by running the linked flow inside the Automation Platform.

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Automation Platform tools

Need more complex logic? Create an Automation Platform tool and Autocalls builds and links the flow for you — no manual webhook setup required.
When you set the tool type to Automation Platform, Autocalls automatically creates a connected flow in the Automation Platform and wires the tool’s endpoint to it. The endpoint and method are generated and locked, so they can’t accidentally be changed.
1

Create the tool

Choose the Automation Platform type, give the tool a name, description and parameters. On save, the linked flow is created automatically.
2

Open the flow

On the tool’s edit page, the connection card shows the flow status (Live/Disabled) and an Open flow in Automation Platform button. The flow starts from a webhook trigger and ends with a Return Response step.
3

Build your logic

Add steps between the trigger and the response — API calls, CRM updates, branching, data transforms — then keep a Return Response step so the AI receives a result.
4

Keep parameters in sync

If you change the tool’s parameters or static fields, use Resync sample data so the flow’s trigger sample matches. If the initial flow creation ever fails, a Retry flow creation button appears on the edit page.
This lets you:
  • Transform data before/after API calls
  • Make multiple API calls in sequence
  • Apply complex business logic
  • Handle errors gracefully
Prefer to wire it up yourself? You can still use a plain HTTP request tool pointed at an existing Automation Platform webhook URL with /sync appended (e.g. https://automate.autocalls.ai/api/v1/webhooks/abc123/sync).

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Real-World Examples

Name: check_order
Endpoint: https://api.yourshop.com/orders/{order_number}
Parameters:
  - Name: order_number
    Type: string
    Description: "Order reference (format: ORD-XXXXX)"
The AI will:
  1. Ask for the order number
  2. Fetch the status
  3. Explain delivery dates and status to the customer
Name: check_slots
Endpoint: https://api.calendar.com/availability
Parameters:
  - Name: service
    Type: string
    Description: "Service type (haircut, massage, consultation)"
  - Name: date
    Type: string
    Description: "Preferred date (dd/mm/yyyy)"
The AI will:
  1. Ask about the desired service
  2. Get preferred date
  3. Show available time slots
Name: verify_customer
Endpoint: https://api.crm.com/verify
Parameters:
  - Name: phone
    Type: string
    Description: "10-digit phone number"
  - Name: email
    Type: string
    Description: "Email address for verification"
The AI will:
  1. Collect contact details
  2. Verify against your CRM
  3. Proceed based on verification status

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Configuring Your AI

The AI needs clear instructions in its system prompt to effectively use your custom tools.
Example prompt section: 
When to use check_order tool:
1. Customer asks about order status
2. Mentions tracking or delivery
3. Wants to know where their package is

How to use it:
1. Ask for order number if not provided
2. Verify format (ORD-XXXXX)
3. Use tool to fetch status
4. Explain results in simple terms
Test your tools with various conversation flows to ensure the AI handles all scenarios smoothly. Start with simple test calls before going live.