▸ Agent Skills
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Documentation Index

Fetch the complete documentation index at: https://agentclientprotocol.com/llms.txt Use this file to discover all available pages before exploring further.

Content

Understanding content blocks in the Agent Client Protocol

Content blocks represent displayable information that flows through the Agent Client Protocol. They provide a structured way to handle various types of user-facing content—whether it’s text from language models, images for analysis, or embedded resources for context.

Content blocks appear in:

Content Types

The Agent Client Protocol uses the same ContentBlock structure as the Model Context Protocol (MCP).

This design choice enables Agents to seamlessly forward content from MCP tool outputs without transformation.

Text Content

Plain text messages form the foundation of most interactions.

{
  "type": "text",
  "text": "What's the weather like today?"
}

All Agents MUST support text content blocks when included in prompts.

The text content to display Optional metadata about how the content should be used or displayed. [Learn more](https://modelcontextprotocol.io/specification/2025-06-18/server/resources#annotations).

Image Content

Images can be included for visual context or analysis.

{
  "type": "image",
  "mimeType": "image/png",
  "data": "iVBORw0KGgoAAAANSUhEUgAAAAEAAAAB..."
}

Requires the image prompt capability when included in prompts.

Base64-encoded image data The MIME type of the image (e.g., "image/png", "image/jpeg") Optional URI reference for the image source Optional metadata about how the content should be used or displayed. [Learn more](https://modelcontextprotocol.io/specification/2025-06-18/server/resources#annotations).

Audio Content

Audio data for transcription or analysis.

{
  "type": "audio",
  "mimeType": "audio/wav",
  "data": "UklGRiQAAABXQVZFZm10IBAAAAABAAEAQB8AAAB..."
}

Requires the audio prompt capability when included in prompts.

Base64-encoded audio data The MIME type of the audio (e.g., "audio/wav", "audio/mp3") Optional metadata about how the content should be used or displayed. [Learn more](https://modelcontextprotocol.io/specification/2025-06-18/server/resources#annotations).

Embedded Resource

Complete resource contents embedded directly in the message.

{
  "type": "resource",
  "resource": {
    "uri": "file:///home/user/script.py",
    "mimeType": "text/x-python",
    "text": "def hello():\n    print('Hello, world!')"
  }
}

This is the preferred way to include context in prompts, such as when using @-mentions to reference files or other resources.

By embedding the content directly in the request, Clients can include context from sources that the Agent may not have direct access to.

Requires the embeddedContext prompt capability when included in prompts.

The embedded resource contents, which can be either: The URI identifying the resource 
<ParamField path="text" type="string" required>
  The text content of the resource
</ParamField>

<ParamField path="mimeType" type="string">
  Optional MIME type of the text content
</ParamField>
 The URI identifying the resource 
<ParamField path="blob" type="string" required>
  Base64-encoded binary data
</ParamField>

<ParamField path="mimeType" type="string">
  Optional MIME type of the blob
</ParamField>
 Optional metadata about how the content should be used or displayed. [Learn more](https://modelcontextprotocol.io/specification/2025-06-18/server/resources#annotations).

References to resources that the Agent can access.

{
  "type": "resource_link",
  "uri": "file:///home/user/document.pdf",
  "name": "document.pdf",
  "mimeType": "application/pdf",
  "size": 1024000
}
The URI of the resource A human-readable name for the resource The MIME type of the resource Optional display title for the resource Optional description of the resource contents Optional size of the resource in bytes Optional metadata about how the content should be used or displayed. [Learn more](https://modelcontextprotocol.io/specification/2025-06-18/server/resources#annotations).

Last updated Oct 08, 2026