Client API

The Client struct is used to connect to MCP servers and send MCP requests.

Constructor

Client.init

pub fn init(io: std.Io, allocator: std.mem.Allocator, config: ClientConfig) Client

Create a new MCP client. The io and allocator are stored internally and reused for all operations.

Config fields:

Field	Type	Description
name	[]const u8	Client name (required)
version	[]const u8	Client version (required)
title	?[]const u8	Optional human-readable title
description	?[]const u8	Optional description
icons	?[]const mcp.types.Icon	Optional icon list
websiteUrl	?[]const u8	Optional website URL

Example:

var client: mcp.Client = .init(io, allocator, .{
    .name = "my-client",
    .version = "1.0.0",
});
defer client.deinit();

---

Lifecycle

Client.deinit

pub fn deinit(self: *Client) void

Clean up client resources and pending state.

---

Capabilities

pub fn enableRoots(self: *Client, listChanged: bool) void
pub fn enableSampling(self: *Client) void
pub fn enableSamplingAdvanced(self: *Client, context: bool, tools_support: bool) void
pub fn enableElicitation(self: *Client) void
pub fn enableElicitationForm(self: *Client) void
pub fn enableElicitationUrl(self: *Client) void
pub fn enableTasks(self: *Client) void
pub fn enableTasksAdvanced(self: *Client, sampling: bool, elicitation: bool) void

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Roots Management

pub fn addRoot(self: *Client, uri: []const u8, name: ?[]const u8) !void

---

Connection Management

pub fn connectStdio(self: *Client, command: []const u8, args: []const []const u8) !void
pub fn connectHttp(self: *Client, url: []const u8) !void
pub fn setAuthorizationToken(self: *Client, token: []const u8) !void
pub fn disconnect(self: *Client) void

connectHttp expects the full MCP endpoint URL, e.g. http://127.0.0.1:8080/mcp (server exposes POST /mcp).

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Request APIs

All request APIs send JSON-RPC messages and return !void. The io and allocator are reused from initialization.

pub fn discover(self: *Client) !void

pub fn listTools(self: *Client) !void
pub fn callTool(self: *Client, name: []const u8, arguments: ?std.json.Value) !void

pub fn listResources(self: *Client) !void
pub fn readResource(self: *Client, uri: []const u8) !void
pub fn subscriptionsListen(self: *Client, uri: []const u8) !void
pub fn listResourceTemplates(self: *Client) !void

pub fn listPrompts(self: *Client) !void
pub fn getPrompt(self: *Client, name: []const u8, arguments: ?std.json.Value) !void

pub fn complete(self: *Client, ref: std.json.Value, argument: std.json.Value) !void

pub fn getTask(self: *Client, taskId: []const u8) !void
pub fn getTaskResult(self: *Client, taskId: []const u8) !void
pub fn listTasks(self: *Client) !void
pub fn cancelTask(self: *Client, taskId: []const u8) !void

pub fn notifyRootsChanged(self: *Client) !void

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Minimal Example

const std = @import("std");
const mcp = @import("mcp");

pub fn main(init: std.process.Init) void {
    run(init.io, init.gpa) catch |err| mcp.reportError(err);
}

fn run(io: std.Io, allocator: std.mem.Allocator) !void {
    var client: mcp.Client = .init(io, allocator, .{
        .name = "full-client",
        .version = "1.0.0",
    });
    defer client.deinit();

    client.enableRoots(true);
    client.enableSamplingAdvanced(true, true);

    try client.addRoot("file:///home/user/docs", "Documentation");
    try client.addRoot("file:///home/user/code", "Source Code");
}