mcp_client/manager

MCP Manager — manages multiple MCP server connections.

Provides unified tool, resource, and prompt discovery and execution across multiple MCP servers. Each server is configured with a command and args; the manager handles lifecycle, discovery, and routing via JSON-RPC 2.0 over STDIO.

Usage

let assert Ok(mgr) = manager.start()
let config = manager.ServerConfig(name: "fs", command: "npx", args: [...], env: [], retry: manager.NoRetry)
manager.register(mgr, config)

Types

ManagerMessage

</>

Messages for the manager actor.

pub type ManagerMessage {
  RegisterServer(
    reply_to: process.Subject(Result(Nil, String)),
    config: ServerConfig,
  )
  UnregisterServer(
    reply_to: process.Subject(Result(Nil, String)),
    name: String,
  )
  ListServers(reply_to: process.Subject(List(String)))
  GetServerConfig(
    reply_to: process.Subject(Result(ServerConfig, String)),
    name: String,
  )
  ListTools(reply_to: process.Subject(List(Tool)))
  ExecuteTool(
    reply_to: process.Subject(Result(String, String)),
    tool_name: String,
    args: String,
  )
  ListResources(reply_to: process.Subject(List(Resource)))
  ReadResource(
    reply_to: process.Subject(Result(String, String)),
    server_name: String,
    uri: String,
  )
  ListPrompts(reply_to: process.Subject(List(Prompt)))
  GetPrompt(
    reply_to: process.Subject(Result(String, String)),
    server_name: String,
    name: String,
    args: dict.Dict(String, String),
  )
  Stop(reply_to: process.Subject(Nil))
}

Constructors

RegisterServer(
  reply_to: process.Subject(Result(Nil, String)),
  config: ServerConfig,
)

UnregisterServer(
  reply_to: process.Subject(Result(Nil, String)),
  name: String,
)

ListServers(reply_to: process.Subject(List(String)))

GetServerConfig(
  reply_to: process.Subject(Result(ServerConfig, String)),
  name: String,
)

ListTools(reply_to: process.Subject(List(Tool)))

ExecuteTool(
  reply_to: process.Subject(Result(String, String)),
  tool_name: String,
  args: String,
)

ListResources(reply_to: process.Subject(List(Resource)))

ReadResource(
  reply_to: process.Subject(Result(String, String)),
  server_name: String,
  uri: String,
)

ListPrompts(reply_to: process.Subject(List(Prompt)))

GetPrompt(
  reply_to: process.Subject(Result(String, String)),
  server_name: String,
  name: String,
  args: dict.Dict(String, String),
)

```
Stop(reply_to: process.Subject(Nil))
```

McpManager

</>

The manager handle.

pub type McpManager =
  process.Subject(ManagerMessage)

Prompt

</>

A discovered prompt template from an MCP server.

pub type Prompt {
  Prompt(
    name: String,
    description: String,
    server_name: String,
    arguments: List(PromptArg),
  )
}

Constructors

```
Prompt(
  name: String,
  description: String,
  server_name: String,
  arguments: List(PromptArg),
)
```
Arguments

name

Prompt name.

description

Human-readable description.

server_name

Which server provides this prompt.

arguments

Argument definitions.

PromptArg

</>

An argument definition for an MCP prompt.

pub type PromptArg {
  PromptArg(name: String, description: String, required: Bool)
}

Constructors

PromptArg(name: String, description: String, required: Bool)

Resource

</>

A discovered resource from an MCP server.

pub type Resource {
  Resource(
    uri: String,
    name: String,
    description: String,
    server_name: String,
  )
}

Constructors

```
Resource(
  uri: String,
  name: String,
  description: String,
  server_name: String,
)
```
Arguments

uri

Resource URI (e.g. “file:///path/to/file”).

name

Human-readable name.

description

Human-readable description.

server_name

Which server provides this resource.

RetryPolicy

</>

Retry policy applied when a server process crashes.

pub type RetryPolicy {
  NoRetry
  Retry(max_attempts: Int, base_delay_ms: Int)
}

Constructors

```
NoRetry
```
Remove the server from state immediately on crash.
```
Retry(max_attempts: Int, base_delay_ms: Int)
```
Retry up to max_attempts times with exponential backoff starting at base_delay_ms milliseconds.

ServerConfig

</>

Configuration for an MCP server connection.

pub type ServerConfig {
  ServerConfig(
    name: String,
    command: String,
    args: List(String),
    env: List(#(String, String)),
    retry: RetryPolicy,
  )
}

Constructors

```
ServerConfig(
  name: String,
  command: String,
  args: List(String),
  env: List(#(String, String)),
  retry: RetryPolicy,
)
```
Arguments

name

Unique name for this server.

command

Command to execute (e.g. “npx”, “node”, “python3”).

args

Command arguments.

env

Environment variables.

retry

What to do if the server process crashes.

Tool

</>

A discovered tool from an MCP server.

pub type Tool {
  Tool(
    spec: ToolSpec,
    server_name: String,
    original_name: String,
  )
}

Constructors

```
Tool(spec: ToolSpec, server_name: String, original_name: String)
```
Arguments

spec

Qualified name: “server_name/tool_name”.

server_name

Which server provides this tool.

original_name

Original tool name as declared by the MCP server.

ToolSpec

</>

Minimal tool specification (name + description).

pub type ToolSpec {
  ToolSpec(name: String, description: String)
}

Constructors

ToolSpec(name: String, description: String)

Values

execute_tool

</>

pub fn execute_tool(
  manager: process.Subject(ManagerMessage),
  tool_name: String,
  args: String,
) -> Result(String, String)

Execute a tool by qualified name ("server/tool") with JSON arguments.

get_prompt

</>

pub fn get_prompt(
  manager: process.Subject(ManagerMessage),
  server_name: String,
  name: String,
  args: dict.Dict(String, String),
) -> Result(String, String)

Get a rendered prompt by name from a named server. Returns the raw JSON result.

get_server

</>

pub fn get_server(
  manager: process.Subject(ManagerMessage),
  name: String,
) -> Result(ServerConfig, String)

Get a server’s configuration by name.

list_prompts

</>

pub fn list_prompts(
  manager: process.Subject(ManagerMessage),
) -> List(Prompt)

List all prompts discovered across all servers.

list_resources

</>

pub fn list_resources(
  manager: process.Subject(ManagerMessage),
) -> List(Resource)

List all resources discovered across all servers.

list_servers

</>

pub fn list_servers(
  manager: process.Subject(ManagerMessage),
) -> List(String)

List all registered server names.

list_tools

</>

pub fn list_tools(
  manager: process.Subject(ManagerMessage),
) -> List(Tool)

List all discovered tools across all servers.

read_resource

</>

pub fn read_resource(
  manager: process.Subject(ManagerMessage),
  server_name: String,
  uri: String,
) -> Result(String, String)

Read a resource by URI from a named server. Returns the raw JSON result.

register

</>

pub fn register(
  manager: process.Subject(ManagerMessage),
  config: ServerConfig,
) -> Result(Nil, String)

Register an MCP server. Starts the process, performs the MCP initialize handshake, and discovers all tools, resources, and prompts.

start

</>

pub fn start() -> Result(
  process.Subject(ManagerMessage),
  actor.StartError,
)

Start a new MCP manager.

stop

</>

pub fn stop(manager: process.Subject(ManagerMessage)) -> Nil

Stop the manager and all server connections.

unregister

</>

pub fn unregister(
  manager: process.Subject(ManagerMessage),
  name: String,
) -> Result(Nil, String)

Unregister an MCP server and stop its process.

Usage

Constructors

Constructors

Arguments

Constructors

Constructors

Arguments

Constructors

Constructors

Arguments

Constructors

Arguments

Constructors