PluMCP Client

The PluMCP client workflow:

flowchart TD
    Start@{ shape: circle, label: "Start" }
    A@{ shape: rounded, label: "1. Make PluMCP client" }
    B@{ shape: rounded, label: "2. Initialize" }
    C@{ shape: rounded, label: "3. MCP client operation" }
    D@{ shape: rounded, label: "4. Disconnect" }
    Stop@{ shape: dbl-circ, label: "Stop" }
    Start-->A
    A-->|Transport is started|B
    B-->|Session is established|C
    C-->|Next MCP Client Operation| C
    C-->|Want to end the client|D
    D-->|Session/Transport is stopped|Stop

The PluMCP Client API is contained in the plumcp.core.api.mcp-client namespace. Remainder of this page assumes you have these aliases setup.

(ns app.core
  (:require [plumcp.core.api.entity-support :as es]
            [plumcp.core.api.mcp-client :as mc]
            [plumcp.core.client.http-client-transport :as hct]
            [plumcp.core.client.stdio-client-transport :as sct]
            [plumcp.core.support.http-client :as hc]))

1. Make PluMCP client

(def client-info (es/make-info "My MCP app" "0.1.0"))

(def stdio-transport
  (sct/run-command {:command-tokens ["run-mcp-server"]}))

(def http-transport
  (hct/make-streamable-http-transport
   ((hc/make-http-client "http://localhost:3000/mcp"))))

(def client-transport http-transport)  ; or stdio-transport

(def the-client (mc/make-client {:info client-info
                                 :client-transport client-transport}))

2. Initialize the client

MCP client initialization needs to be followed up with a notification of initialization, which you can do as follows:

(mc/initialize-and-notify! the-client)

If you want control over how/when notification happens, or you want to perform some step before sending notification, you may use the lower level API:

(mc/initialize! the-client
                (fn [result]
                  (mc/notify-initialized the-client)))

3. MCP Client operation

The MCP Client operations have their corresponding API. Some of the API calls that accept client and a handler function as argument are shown below:

MCP Client Operation	Client API call	Arguments
List MCP prompts	`mc/list-prompts`	`[client handler]`
List MCP resources	`mc/list-resources`	`[client handler]`
List MCP resource templates	`mc/list-resource-templates`	`[client handler]`
List MCP tools	`mc/list-tools`	`[client handler]`
Get MCP prompt	`mc/get-prompt`	`[client handler]`
Read MCP resource	`mc/read-resource`	`[client handler]`
Call MCP tool	`mc/call-tool`	`[client handler]`
Complete (Completion)	`mc/complete`	`[client handler]`
Ping	`mc/ping`	`[client handler]`

Note!

This is a selected list of API calls - for exhaustive list check the source in plumcp.core.api.mcp-client namespace.

For example, you can print the list the MCP tools as follows:

(mc/list-tools the-client (fn [tools]
                            (println "Tools" tools)))

The handler is an arity-1 callback function that is invoked after the response for the client request arrives.

4. Disconnect the client

Disconnection of the client, which stops the transport, is quite straightforward:

(mc/disconnect! the-client)

Don't forget to disconnect

Failing to disconnect the PluMCP client may keep the client transport running, holding on to resources, hence preventing cleanup.