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Built-in tools (also called system tools) are tools that msg.Hello ships with itself. They are automatically available in every agent, need no connector, no base URL, and no credentials, and they talk to no external system. Their logic runs entirely on the platform.
Because built-in tools are available without configuration, they do not appear in the connector selection. You enable them directly in the flow at the respective state.

classify – classify the request

The central built-in tool is classify. With it the agent assigns the caller’s request to exactly one of the categories you have defined. The chosen category becomes the response code on which your flow transitions branch.

What it does

Picks the matching one from your categories (e.g. termin, rezept, sonstiges) and returns it as a branching code.

When the agent calls it

Only once the category is unambiguously established. When in doubt, the agent keeps asking instead of guessing.

How you use it in the flow

1

Define categories

Set the allowed categories at a state – these are the possible results of the classification.
2

Link transitions

Connect each category to the target state the agent should switch to for that request.
3

Test

Check with a test call whether typical requests are classified correctly.
classify is fully live. It works locally and without side effects: no external call, no database, no stored states.

get_caller_phone_number – get the caller’s number

With get_caller_phone_number (shown in the portal as Anrufernummer abrufen), the agent reads the phone number of the current caller. This way the caller doesn’t have to dictate their number, for example for a callback or for matching in your business system. The tool needs no parameters. The agent only calls it when it actually needs the number in the conversation. Enable the tool in the flow at the state where the number is needed, and branch on the response codes if required.
This tool also works without an external call. It only reads the phone number transmitted with the call.

Distinction: forwarding & hanging up

Forwarding to a human and hanging up are not tools but terminal states in the flow. They also work without any integration. Details on this in the Building flows chapter.
A useful entry-level agent combines only built-in capabilities: greet, recognize the request with classify, and forward if needed. You build out domain-specific automation via connectors or MCP servers afterwards, step by step.