How to define resources in an MCP server

1// TypeScript
2import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
3
4const server = new McpServer({ name: "resource-server", version: "1.0.0" });
5
6server.registerResource("app-config", "config://app", {
7  description: "Application configuration settings",
8  mimeType: "application/json",
9}, async (uri) => ({
10  contents: [{
11    uri: uri.href,
12    text: JSON.stringify({
13      appName: "My App",
14      version: "2.1.0",
15      features: ["auth", "billing", "notifications"],
16    }, null, 2),
17  }],
18}));
19
20# Python
21from mcp.server.fastmcp import FastMCP
22
23mcp = FastMCP("resource-server")
24
25@mcp.resource("config://app")
26async def get_app_config() -> str:
27    """Application configuration settings."""
28    return json.dumps({
29        "appName": "My App",
30        "version": "2.1.0",
31        "features": ["auth", "billing", "notifications"],
32    }, indent=2)

1// TypeScript
2import { ResourceTemplate } from "@modelcontextprotocol/sdk/server/mcp.js";
3
4server.registerResourceTemplate(
5  "user-profile",
6  new ResourceTemplate("db://users/{userId}", { list: undefined }),
7  {
8    description: "User profile data by ID",
9    mimeType: "application/json",
10  },
11  async (uri, { userId }) => {
12    const user = await db.query("SELECT * FROM users WHERE id = $1", [userId]);
13    return {
14      contents: [{
15        uri: uri.href,
16        text: JSON.stringify(user, null, 2),
17      }],
18    };
19  }
20);
21
22# Python
23@mcp.resource("db://users/{user_id}")
24async def get_user_profile(user_id: str) -> str:
25    """User profile data by ID."""
26    user = await db.fetchrow("SELECT * FROM users WHERE id = $1", user_id)
27    return json.dumps(dict(user), indent=2)

1// TypeScript
2import { readFile } from "fs/promises";
3import path from "path";
4
5const PROJECT_ROOT = "/home/user/project";
6
7server.registerResourceTemplate(
8  "project-file",
9  new ResourceTemplate("file://project/{filePath+}", { list: undefined }),
10  { description: "Project source files" },
11  async (uri, { filePath }) => {
12    // Prevent directory traversal
13    const resolved = path.resolve(PROJECT_ROOT, filePath as string);
14    if (!resolved.startsWith(PROJECT_ROOT)) {
15      throw new Error("Access denied: path outside project root");
16    }
17    const content = await readFile(resolved, "utf-8");
18    return {
19      contents: [{ uri: uri.href, text: content }],
20    };
21  }
22);

1// TypeScript
2import { readFile } from "fs/promises";
3
4server.registerResource("app-logo", "assets://logo.png", {
5  description: "Application logo image",
6  mimeType: "image/png",
7}, async (uri) => {
8  const buffer = await readFile("./assets/logo.png");
9  return {
10    contents: [{
11      uri: uri.href,
12      blob: buffer.toString("base64"),
13    }],
14  };
15});

1// Resources for reading
2server.registerResource("schema", "db://schema", {
3  description: "Database schema definition",
4}, async (uri) => ({
5  contents: [{ uri: uri.href, text: await getSchemaSQL() }],
6}));
7
8// Tools for writing
9server.registerTool("run-query", {
10  description: "Execute a read-only SQL query",
11  inputSchema: { sql: z.string() },
12}, async ({ sql }) => {
13  const result = await pool.query(sql);
14  return { content: [{ type: "text", text: JSON.stringify(result) }] };
15});