URL: https://gofastmcp.com/clients/client-only-package
Title: Client-Only Package - FastMCP

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Supported Usage
When to Use the Full Package
Clients
Client-Only Package
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Use FastMCP’s client without installing the full server framework.
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New in version
3.3.0
FastMCP’s full
fastmcp
package includes everything needed to build and run MCP servers, apps, proxies, and clients. If you are only embedding an MCP client in another framework, building your own LLM host, or testing MCP servers, you can install the smaller client-only package instead.
pip
install
"
fastmcp-slim[client]
"
The client-only package uses the
fastmcp
import namespace:
from
fastmcp
import
Client
client
=
Client
(
"
https://example.com/mcp
"
)
Use
fastmcp-slim[client]
when your code connects to MCP servers but does not define or run FastMCP servers itself. For example, framework authors can depend on
fastmcp-slim[client]
to provide MCP connectivity without requiring users to install the full FastMCP server stack.
​
Supported Usage
Client-only installs support remote and subprocess transports:
from
fastmcp
import
Client
# Remote MCP server
http_client
=
Client
(
"
https://example.com/mcp
"
)
# Local MCP server over stdio
stdio_client
=
Client
(
"
my_server.py
"
)
Single-server MCP configuration works as well:
from
fastmcp
import
Client
config
=
{
"
mcpServers
"
:
{
"
weather
"
:
{
"
url
"
:
"
https://weather.example.com/mcp
"
}
}
}
client
=
Client
(
config
)
Optional sampling handlers are available through the same extras as the full package:
pip
install
"
fastmcp-slim[client,openai]
"
pip
install
"
fastmcp-slim[client,anthropic]
"
pip
install
"
fastmcp-slim[client,gemini]
"
​
When to Use the Full Package
Install
fastmcp
when you need server-side FastMCP features:
pip
install
fastmcp
The full package remains the default for most users and continues to support the existing import style:
from
fastmcp
import
Client
,
FastMCP
server
=
FastMCP
(
"
Example
"
)
client
=
Client
(
server
)
Use the full package for:
defining or running FastMCP servers
in-memory clients connected directly to
FastMCP
server objects
multi-server MCP configurations
FastMCP apps, proxies, server auth, middleware, and other server-side features
The
fastmcp-slim
package is intentionally narrower: it is for client-only consumers who want FastMCP’s MCP client behavior without depending on the full framework.
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