repro.zig

const std = @import("std");
const json = std.json;

pub const ContentType = enum {
    text,
    image,
    resource,
};

pub const CallToolResult = struct {
    isError: bool = false,
    content: []const Content,
};

/// A content response.
/// For text content set type to ContentType.Text and set the `text` property
/// For image content set type to ContentType.Image and set the `data` and `mimeType` properties
pub const Content = struct {
    type: ?ContentType = ContentType.text,
    text: ?[]const u8 = null,
    data: ?[]const u8 = null,
    mimeType: ?[]const u8 = null,
};

const allocator = std.heap.page_allocator;

pub fn main() !void {
    const stdout_file = std.io.getStdOut().writer();
    const r = try getResult();

    try json.stringify(r, .{}, stdout_file);
}

fn getResult() !CallToolResult {
    const msg = try std.fmt.allocPrint(
        allocator,
        "Error {d}: {s}",
        .{ 404, "Not Found" },
    );

    return CallToolResult{ .content = &.{.{ .text = msg }} };
}