LangChain.MCP.ContentMapper (LangChain MCP v0.2.0)

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Maps MCP content arrays to LangChain ContentPart structures.

MCP tool responses contain a content array with multi-modal content items. This module converts them to LangChain's ContentPart format for use in messages and tool results.

MCP Content Types

MCP supports these content types:

  • text - Plain text content
  • image - Base64 encoded image data with mimeType
  • resource - Reference to a resource (file, URL, etc.)

LangChain ContentPart Types

These are mapped to:

  • :text - Text content
  • :image - Base64 image with media type
  • :file - File data (for resources)
  • :unsupported - For unknown types

Examples

# Text content
mcp_content = [%{"type" => "text", "text" => "Hello world"}]
parts = ContentMapper.to_content_parts(mcp_content)
# => [%ContentPart{type: :text, content: "Hello world"}]

# Image content
mcp_content = [
  %{"type" => "image", "data" => "base64data...", "mimeType" => "image/png"}
]
parts = ContentMapper.to_content_parts(mcp_content)
# => [%ContentPart{type: :image, content: "base64data...", options: [media: "image/png"]}]

# Mixed content
mcp_content = [
  %{"type" => "text", "text" => "See this image:"},
  %{"type" => "image", "data" => "...", "mimeType" => "image/jpeg"}
]
parts = ContentMapper.to_content_parts(mcp_content)
# => [%ContentPart{type: :text, ...}, %ContentPart{type: :image, ...}]

Summary

Functions

extract_text(mcp_content)

Extracts just the text content from an MCP content array.

from_content_parts(content_parts)

Converts LangChain ContentParts back to MCP content format.

has_images?(mcp_content)

Checks if MCP content contains any images.

has_text?(mcp_content)

Checks if MCP content contains any text.

to_content_parts(mcp_content)

Converts an MCP content array to a list of ContentPart structs.

Functions

extract_text(mcp_content)

@spec extract_text([map()]) :: String.t() | nil

Extracts just the text content from an MCP content array.

Useful when you only care about text responses and want to ignore other content types.

Parameters

  • mcp_content - List of MCP content items

Returns

  • String of concatenated text content, or nil if no text found

Examples

iex> mcp_content = [
...>   %{"type" => "text", "text" => "Hello "},
...>   %{"type" => "text", "text" => "world"},
...>   %{"type" => "image", "data" => "..."}
...> ]
iex> ContentMapper.extract_text(mcp_content)
"Hello world"

from_content_parts(content_parts)

@spec from_content_parts([LangChain.Message.ContentPart.t()]) :: [map()]

Converts LangChain ContentParts back to MCP content format.

This is useful for testing or when you need to send content back to an MCP server.

Parameters

  • content_parts - List of ContentPart structs

Returns

  • List of MCP content maps

has_images?(mcp_content)

@spec has_images?([map()]) :: boolean()

Checks if MCP content contains any images.

Examples

iex> mcp_content = [%{"type" => "image", "data" => "..."}]
iex> ContentMapper.has_images?(mcp_content)
true

has_text?(mcp_content)

@spec has_text?([map()]) :: boolean()

Checks if MCP content contains any text.

Examples

iex> mcp_content = [%{"type" => "text", "text" => "Hello"}]
iex> ContentMapper.has_text?(mcp_content)
true

iex> mcp_content = [%{"type" => "image", "data" => "..."}]
iex> ContentMapper.has_text?(mcp_content)
false

to_content_parts(mcp_content)

@spec to_content_parts([map()]) :: [LangChain.Message.ContentPart.t()]

Converts an MCP content array to a list of ContentPart structs.

Parameters

  • mcp_content - List of MCP content items (maps)

Returns

  • List of ContentPart.t() structs

Examples

iex> mcp_content = [%{"type" => "text", "text" => "Result"}]
iex> [part] = ContentMapper.to_content_parts(mcp_content)
iex> part.type
:text
iex> part.content
"Result"