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

# Agent Tools

> How an agent reaches your apps, your flows, and your systems

Tools are how an agent reaches the rest of your company, and it uses them two ways.

**To find out.** It searches Slack, Linear, Drive, or any of 760+ apps at the moment it needs the answer, rather than working from whatever you pasted into the instructions.

**To act.** It raises the invoice, drafts the document, updates the record.

Attach none and it can only talk.

<CardGroup cols={3}>
  <Card title="Piece tool" icon="puzzle-piece" color="#8143E3">
    A single action from one of your connected apps.
  </Card>

  <Card title="Flow tool" icon="sitemap" color="#16A34A">
    One of your own flows, handed over as a tool.
  </Card>

  <Card title="MCP server" icon="plug" color="#0EA5E9">
    An external server, for systems that aren't pieces.
  </Card>
</CardGroup>

## Piece tools

You attach individual actions, not whole apps. An agent given **Send message** can post to Slack and nothing else.

Each input on that action is one of three modes, so you pin what has to be exact and leave the rest to the agent.

<CardGroup cols={3}>
  <Card title="Let agent decide" icon="wand-magic-sparkles" color="#8143E3">
    It writes the value.
  </Card>

  <Card title="Set value myself" icon="thumbtack" color="#0EA5E9">
    You pin it.
  </Card>

  <Card title="Leave empty" icon="ban" color="#64748B">
    Nothing is sent.
  </Card>
</CardGroup>

Pin the Slack channel, let the agent write the message.

## Flow tools

The most underused one. When part of a job has to happen the same way every time, build that part as a flow and hand it over.

The agent chooses the moment. The flow guarantees the steps.

## MCP servers

Paste the URL and pick how it authenticates: none, an access token, an API key, or custom headers. Streamable HTTP, SSE, and plain HTTP all work.

Activepieces lists the server's tools as soon as you add it, so you know it works before an agent depends on it.

<Tip>
  When an agent keeps getting something wrong, ask what it was missing. Usually it needed somewhere to look something up, not a longer prompt.
</Tip>