> ## Documentation Index
> Fetch the complete documentation index at: https://explore.airia.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Extending Airia Agent

> Choose the right approach — tools, MCP servers, or sub-agents — before you start configuring.

Airia Agent supports two complementary ways to extend its capabilities. Before you visit the **Tools** or **Sub-agents** tabs, use this guide to pick the right approach for each capability you want to add.

## The two approaches

### Tools and MCP servers

Tools are discrete, callable actions: search a knowledge base, query a database, call an external API, run a code snippet. You attach them directly to Airia Agent, and it invokes them as needed during a conversation.

MCP (Model Context Protocol) servers are a standardized way to expose multiple tools from a single external server. Connecting an MCP server makes all of its tools available to Airia Agent at once.

**Use tools or MCP servers when:**

* The capability is a single, well-defined action (fetch, query, write, execute)
* You want low-latency access to a frequently used integration
* The tool does not require its own persona, conversation context, or specialized reasoning

### Sub-agents

Sub-agents are fully built Airia agents from your catalog that Airia Agent can invoke during a conversation. When Airia Agent determines a task is best handled by a specialized agent, it delegates the conversation turn to that agent and returns the result.

**Use sub-agents when:**

* You already have a purpose-built agent (e.g., an HR assistant, a code reviewer) that should remain independently accessible in the catalog
* The capability requires multi-step reasoning, its own system prompt, or specialized knowledge
* You want to route requests between distinct domains without exposing multiple entry points to end users

## Decision guide

| What you want to do                                                         | Recommended approach |
| --------------------------------------------------------------------------- | -------------------- |
| Call an external REST API                                                   | Tool                 |
| Query a database                                                            | Tool                 |
| Execute code in the sandbox                                                 | Tool                 |
| Use an external MCP server (e.g., a file system, browser, or custom server) | MCP server           |
| Delegate to an existing HR bot                                              | Sub-agent            |
| Delegate to an existing code-review agent                                   | Sub-agent            |
| Reuse an agent end users also access directly from the catalog              | Sub-agent            |
| Add a capability that needs its own persona or specialized knowledge        | Sub-agent            |

## Using both together

Tools and sub-agents are additive. Airia Agent has access to all configured tools and all configured sub-agents simultaneously. At runtime, the agent chooses the most appropriate capability based on the user's request.

<Note>
  If you are unsure which approach to use, start with a sub-agent. Tools can always be added later once a capability is built out, tested, and validated as a named agent. Reverting a tool-based approach is harder once users rely on it.
</Note>

***

Ready to configure?

* [Connect tools and MCP servers →](/admin-hub/airia-agent/tools-and-mcp)
* [Configure sub-agents →](/admin-hub/airia-agent/sub-agents)