---
title: "Reference: createDocumentChunkerTool() | Tools & MCP"
description: Documentation for the Document Chunker Tool in Mastra, which splits documents into smaller chunks for efficient processing and retrieval.
packages:
  - "@mastra/rag"
---

# createDocumentChunkerTool()

The `createDocumentChunkerTool()` function creates a tool for splitting documents into smaller chunks for efficient processing and retrieval. It supports different chunking strategies and configurable parameters.

## Basic Usage

```typescript
import { createDocumentChunkerTool, MDocument } from "@mastra/rag";

const document = new MDocument({
  text: "Your document content here...",
  metadata: { source: "user-manual" },
});

const chunker = createDocumentChunkerTool({
  doc: document,
  params: {
    strategy: "recursive",
    size: 512,
    overlap: 50,
    separator: "\n",
  },
});

const { chunks } = await chunker.execute();
```

## Parameters

<PropertiesTable
  content={[
    {
      name: "doc",
      type: "MDocument",
      description: "The document to be chunked",
      isOptional: false,
    },
    {
      name: "params",
      type: "ChunkParams",
      description: "Configuration parameters for chunking",
      isOptional: true,
      defaultValue: "Default chunking parameters",
    },
  ]}
/>

### ChunkParams

<PropertiesTable
  content={[
    {
      name: "strategy",
      type: "'recursive'",
      description: "The chunking strategy to use",
      isOptional: true,
      defaultValue: "'recursive'",
    },
    {
      name: "size",
      type: "number",
      description: "Target size of each chunk in tokens/characters",
      isOptional: true,
      defaultValue: "512",
    },
    {
      name: "overlap",
      type: "number",
      description: "Number of overlapping tokens/characters between chunks",
      isOptional: true,
      defaultValue: "50",
    },
    {
      name: "separator",
      type: "string",
      description: "Character(s) to use as chunk separator",
      isOptional: true,
      defaultValue: "'\\n'",
    },
  ]}
/>

## Returns

<PropertiesTable
  content={[
    {
      name: "chunks",
      type: "DocumentChunk[]",
      description: "Array of document chunks with their content and metadata",
    },
  ]}
/>

## Example with Custom Parameters

```typescript
const technicalDoc = new MDocument({
  text: longDocumentContent,
  metadata: {
    type: "technical",
    version: "1.0",
  },
});

const chunker = createDocumentChunkerTool({
  doc: technicalDoc,
  params: {
    strategy: "recursive",
    size: 1024, // Larger chunks
    overlap: 100, // More overlap
    separator: "\n\n", // Split on double newlines
  },
});

const { chunks } = await chunker.execute();

// Process the chunks
chunks.forEach((chunk, index) => {
  console.log(`Chunk ${index + 1} length: ${chunk.content.length}`);
});
```

## Tool Details

The chunker is created as a Mastra tool with the following properties:

- **Tool ID**: `Document Chunker {strategy} {size}`
- **Description**: `Chunks document using {strategy} strategy with size {size} and {overlap} overlap`
- **Input Schema**: Empty object (no additional inputs required)
- **Output Schema**: Object containing the chunks array

## Related

- [MDocument](../rag/document)
- [createVectorQueryTool](./vector-query-tool)
