Construyendo MCP UI: Widgets Interactivos Dirigidos por el Servidor para Agentes de IA

┌──────────────────────────────────────────────────────────────────┐
│                  AI Agent Client Host (Next.js)                  │
│                                                                  │
│  ┌────────────────────┐       ┌───────────────────────────────┐  │
│  │  LLM Orchestrator  │       │      Dynamic UI Renderer      │  │
│  │  (Vercel AI SDK)   │       │                               │  │
│  └─────────┬──────────┘       │  ┌─────────────────────────┐  │  │
│            │                  │  │     Component Cache     │  │  │
│            │ tools/call       │  └────────────┬────────────┘  │  │
│            ▼                  │               ▼               │  │
│  ┌────────────────────┐       │    [ BlogDiscoveryCard ]      │  │
│  │  MCP Client Layer  │──────►│    [   Action Buttons  ]      │  │
│  │ (JSON-RPC Router)  │◄──────│               │               │  │
│  └─────────┬──────────┘       └───────────────┼───────────────┘  │
│            │                                  │                  │
│            │ JSON-RPC 2.0 (Stdio / SSE)       │                  │
└────────────┼──────────────────────────────────┼──────────────────┘
             │                                  │
             ▼                                  │ UI Action Callback
┌────────────────────────────────────────┐      │ (tools/call: on_select)
│           Custom MCP Server            │      │
│                                        │      │
│  ┌──────────────────────────────────┐  │      │
│  │ Tool: discover_knowledge_node    │  │      │
│  │ ├─ Query Vector / Metadata Store │  │      │
│  │ └─ Generate UI Schema Definition │◄─┴──────┘
│  └──────────────────────────────────┘  │
└────────────────────────────────────────┘

import { Server } from "@modelcontextprotocol/sdk/server/index.js";
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
import {
  CallToolRequestSchema,
  ListToolsRequestSchema,
} from "@modelcontextprotocol/sdk/types.js";

interface KnowledgeArticle {
  title: string;
  slug: string;
  description: string;
  readingTime: number;
  tags: string[];
  coverImage: string;
}

const KNOWLEDGE_BASE: Record<string, KnowledgeArticle> = {
  "mcp-ui-server-driven-interactive-components": {
    title: "Building MCP UI: Server-Driven Interactive Widgets for AI Agents",
    slug: "mcp-ui-server-driven-interactive-components",
    description: "Architecting server-driven generative UI over Model Context Protocol using JSON schemas and sandboxed rendering.",
    readingTime: 8,
    tags: ["MCP", "AI Agents", "Server-Driven UI", "React"],
    coverImage: "/images/blog/mcp-ui-server-driven-interactive-components-cover.png",
  },
};

const server = new Server(
  {
    name: "knowledge-mcp-ui-server",
    version: "1.0.0",
  },
  {
    capabilities: {
      tools: {},
    },
  }
);

// Register Tool Discovery
server.setRequestHandler(ListToolsRequestSchema, async () => {
  return {
    tools: [
      {
        name: "discover_knowledge_node",
        description: "Search technical journal articles and return rich interactive cards.",
        inputSchema: {
          type: "object",
          properties: {
            topic: { type: "string", description: "Search query or keyword" },
            tag: { type: "string", description: "Optional category tag filter" },
          },
          required: ["topic"],
        },
      },
    ],
  };
});

// Handle Tool Execution
server.setRequestHandler(CallToolRequestSchema, async (request) => {
  if (request.params.name !== "discover_knowledge_node") {
    throw new Error(`Unknown tool: ${request.params.name}`);
  }

  const args = request.params.arguments as { topic: string; tag?: string };
  const matchedKey = Object.keys(KNOWLEDGE_BASE).find((key) =>
    key.includes(args.topic.toLowerCase().replace(/\s+/g, "-"))
  ) || "mcp-ui-server-driven-interactive-components";

  const article = KNOWLEDGE_BASE[matchedKey];

  // Construct UI Component Payload
  const uiPayload = {
    component: "BlogDiscoveryCard",
    version: "1.0.0",
    props: {
      title: article.title,
      slug: article.slug,
      description: article.description,
      readingTime: article.readingTime,
      tags: article.tags,
      coverImage: article.coverImage,
    },
    actions: [
      {
        id: "filter_by_tag",
        label: `More on ${article.tags[0]}`,
        tool: "discover_knowledge_node",
        parameters: { topic: article.tags[0], tag: article.tags[0] },
        variant: "secondary" as const,
      },
      {
        id: "open_reader",
        label: "Open Full Post",
        tool: "navigate_route",
        parameters: { href: `/en/journal/${article.slug}` },
        variant: "primary" as const,
      },
    ],
  };

  return {
    content: [
      {
        type: "text",
        text: `Found article: "${article.title}" (${article.readingTime} min read).`,
      },
      {
        type: "resource",
        resource: {
          uri: `ui://knowledge/${article.slug}`,
          mimeType: "application/vnd.mcp.ui+json",
          text: JSON.stringify(uiPayload),
        },
      },
    ],
  };
});

async function main() {
  const transport = new StdioServerTransport();
  await server.connect(transport);
}

main().catch((err) => {
  process.stderr.write(`Server startup failed: ${err.message}\n`);
  process.exit(1);
});

import React from "react";
import Image from "next/image";
import { McpUiAction } from "./types";

interface BlogDiscoveryCardProps {
  title: string;
  slug: string;
  description: string;
  readingTime: number;
  tags: string[];
  coverImage: string;
  actions: McpUiAction[];
  onAction: (action: McpUiAction) => void;
}

export function BlogDiscoveryCard({
  title,
  description,
  readingTime,
  tags,
  coverImage,
  actions,
  onAction,
}: BlogDiscoveryCardProps) {
  return (
    <div style={{ border: "1px solid var(--border-color, #e2e8f0)", borderRadius: 8, padding: 16, background: "var(--surface, #ffffff)" }}>
      {coverImage && (
        <div style={{ position: "relative", width: "100%", height: 160, marginBottom: 12 }}>
          <Image
            src={coverImage}
            alt={title}
            fill
            sizes="(max-width: 768px) 100vw, 400px"
            style={{ objectFit: "cover", borderRadius: 4 }}
          />
        </div>
      )}
      <div style={{ display: "flex", gap: 8, marginBottom: 8 }}>
        {tags.map((tag) => (
          <span key={tag} style={{ fontSize: "0.75rem", background: "#f1f5f9", padding: "2px 8px", borderRadius: 4 }}>
            {tag}
          </span>
        ))}
        <span style={{ fontSize: "0.75rem", color: "#64748b", marginLeft: "auto" }}>
          {readingTime} min read
        </span>
      </div>
      <h3 style={{ margin: "0 0 8px 0", fontSize: "1.1rem" }}>{title}</h3>
      <p style={{ margin: "0 0 16px 0", fontSize: "0.875rem", color: "#475569" }}>{description}</p>
      
      <div style={{ display: "flex", gap: 8 }}>
        {actions.map((act) => (
          <button
            key={act.id}
            onClick={() => onAction(act)}
            style={{
              padding: "6px 12px",
              borderRadius: 4,
              cursor: "pointer",
              fontSize: "0.875rem",
              background: act.variant === "primary" ? "#0f172a" : "#f8fafc",
              color: act.variant === "primary" ? "#ffffff" : "#0f172a",
              border: "1px solid #cbd5e1",
            }}
          >
            {act.label}
          </button>
        ))}
      </div>
    </div>
  );
}

// Registry map
export const COMPONENT_REGISTRY: Record<string, React.ComponentType<any>> = {
  BlogDiscoveryCard,
};

"use client";

import React from "react";
import { McpUiPayloadSchema, McpUiPayload, McpUiAction } from "./types";
import { COMPONENT_REGISTRY } from "./registry";

interface McpToolResource {
  uri: string;
  mimeType: string;
  text: string;
}

interface McpToolResult {
  content: Array<
    | { type: "text"; text: string }
    | { type: "resource"; resource: McpToolResource }
  >;
}

interface McpUiHostProps {
  toolResult: McpToolResult;
  onDispatchTool: (toolName: string, params: Record<string, unknown>) => Promise<void>;
}

export function McpUiHost({ toolResult, onDispatchTool }: McpUiHostProps) {
  // Extract UI resources
  const uiResource = toolResult.content.find(
    (c) => c.type === "resource" && c.resource.mimeType === "application/vnd.mcp.ui+json"
  );

  if (!uiResource || uiResource.type !== "resource") {
    return null;
  }

  let parsedPayload: McpUiPayload;
  try {
    const rawJson = JSON.parse(uiResource.resource.text);
    parsedPayload = McpUiPayloadSchema.parse(rawJson);
  } catch {
    return (
      <div style={{ color: "#dc2626", fontSize: "0.875rem" }}>
        Failed to validate MCP UI component payload.
      </div>
    );
  }

  const TargetComponent = COMPONENT_REGISTRY[parsedPayload.component];
  if (!TargetComponent) {
    return (
      <div style={{ color: "#d97706", fontSize: "0.875rem" }}>
        Unknown component &apos;{parsedPayload.component}&apos; requested by MCP server.
      </div>
    );
  }

  const handleAction = async (action: McpUiAction) => {
    await onDispatchTool(action.tool, action.parameters);
  };

  return (
    <div className="mcp-ui-host-container" style={{ margin: "16px 0" }}>
      <TargetComponent
        {...parsedPayload.props}
        actions={parsedPayload.actions}
        onAction={handleAction}
      />
    </div>
  );
}

import { McpUiPayload } from "./types";

interface KnowledgeArticle {
  title: string;
  slug: string;
  description: string;
  readingTime: number;
  tags: string[];
}

export function buildDualMcpResponse(article: KnowledgeArticle, uiPayload: McpUiPayload) {
  return {
    content: [
      // 1. Terminal / Markdown Fallback (Read by CLI agents)
      {
        type: "text",
        text: [
          `### ${article.title}`,
          `*${article.description}*`,
          `- Reading Time: ${article.readingTime} min`,
          `- Tags: ${article.tags.join(", ")}`,
          `- URL: https://damandeep.dev/en/journal/${article.slug}`,
        ].join("\n"),
      },
      // 2. Rich UI Resource (Rendered by GUI hosts)
      {
        type: "resource",
        resource: {
          uri: `ui://knowledge/${article.slug}`,
          mimeType: "application/vnd.mcp.ui+json",
          text: JSON.stringify(uiPayload),
        },
      },
    ],
  };
}