Resources in MCP Servers

Introduction to Model Context Protocol (MCP)

James Chapman

AI Curriculum Manager, DataCamp

What are MCP Resources?

Chapter 2

Resources + Prompts

What are MCP Resources?

Chapter 2

Resources and prompts
Integration with APIs and databases

Resources: read-only data or data objects retrieved by the MCP client

Not necessarily called by an LLM
Application-Driven → e.g., user preferences
User-Driven → e.g., file upload

MCP Resources in AI Apps

Defining MCP Server Resources

from mcp.server.fastmcp import FastMCP

mcp = FastMCP("Timezone Converter")


@mcp.resource("file://locations.txt")

def get_locations():
    try:
        with open('locations.txt', 'r') as f:
            content = f.read()
        return content
    except FileNotFoundError:
        return "locations.txt file not found"

URI: uniform resource identifier
- Can point to local files, APIs, remote servers, and more
- Can dynamically insert parameters like User ID
locations.txt (server-side) → list of timezone locations

Defining MCP Server Resources

@mcp.resource("file://locations.txt")
def get_locations() -> str:
    """
    Get the list of cities for timezone conversion.

    Returns:
        Contents of the locations.txt file with city names
    """
    try:
        with open('locations.txt', 'r') as f:
            content = f.read()
        return content
    except FileNotFoundError:
        return "locations.txt file not found"

Saving the Server: timezone_server.py

from mcp.server.fastmcp import FastMCP

mcp = FastMCP("Timezone Converter")

# Tools from before...

@mcp.resource("file://locations.txt")
def get_locations() -> str:
    # ...

if __name__ == "__main__":
    mcp.run(transport="stdio")

Client: Listing Resources

async def list_resources():
    """List all available resources from the MCP server."""
    params = StdioServerParameters(command=sys.executable, args=["timezone_server.py"])

    async with stdio_client(params) as (reader, writer):
        async with ClientSession(reader, writer) as session:
            await session.initialize()

            response = await session.list_resources()


            print("Available resources:")
            for resource in response.resources:
                print(f" - {resource.uri}")
                print(f"   Name: {resource.name}")
                print(f"   Description: {resource.description}")

            return response.resources

Client: Listing Resources

print(asyncio.run(list_resources()))

Available resources:
 - file://locations.txt/
   Name: get_locations
   Description: 
    Get the list of cities for timezone conversion.

    Returns:
        Contents of the locations.txt file with city names

[Resource(name='get_locations', title=None, uri=AnyUrl('file://locations.txt/'),
          description='\n    Get the list of cities for timezone conversion.\n\n...',
          mimeType='text/plain', size=None, icons=None, annotations=None, meta=None)]

Client: Reading Resources

async def read_resource(resource_uri: str):
    """Read a specific resource by URI."""
    params = StdioServerParameters(command=sys.executable, args=["timezone_server.py"])

    async with stdio_client(params) as (reader, writer):
        async with ClientSession(reader, writer) as session:
            await session.initialize()


            print(f"Reading resource: {resource_uri}")
            resource_content = await session.read_resource(resource_uri)


            for content in resource_content.contents:
                print(f"\nContent ({content.mimeType}):")
                print(content.text)

            return resource_content

Client: Reading Resources

print(asyncio.run(read_resource('file://locations.txt/')))

Reading resource: file://locations.txt

Content (text/plain):
Africa/Abidjan
Africa/Accra
Africa/Addis_Ababa
Africa/Algiers
...

ReadResourceResult(meta=None, contents=[TextResourceContents(uri=AnyUrl('file://locations.txt/'),
                   mimeType='text/plain', meta=None, text='Africa/Abidjan\nAfrica/Accra...')])

Let's practice!

Introduction to Model Context Protocol (MCP)