Register Resources

MCP has three server primitives. Tools are the ones the model calls; resources and prompts round out the set. A resource is addressable content a host can read by URI: reference docs, a data file, a live-generated report. Where a tool is an action, a resource is a document.

server.ts

import { McpServer } from "skybridge/server";

const server = new McpServer({ name: "shop", version: "1.0" }).registerResource(
  {
    name: "pricing",
    uri: "docs://pricing",
    title: "Pricing",
    description: "Current plan pricing, in Markdown.",
    mimeType: "text/markdown",
  },
  async (uri) => ({
    contents: [{ uri: uri.href, text: await loadPricingDoc() }],
  }),
);

registerResource returns the server, so it chains next to your tool registrations. The handler runs when the host reads the URI and returns the content: text for text, blob (base64) for binary.

Register resources up front, at startup. Adding or removing them at runtime relies on list_changed notifications, which the stateless JSON transport can’t deliver, so hosts won’t see the change.

Static vs. dynamic

A static resource lives at one fixed uri. A dynamic resource uses a template, an RFC 6570 URI template, to cover a family of URIs that share a shape:

server.ts

import { ResourceTemplate } from "@modelcontextprotocol/sdk/server/mcp.js";

server.registerResource(
  {
    name: "order",
    template: new ResourceTemplate("orders://{orderId}", { list: undefined }),
  },
  async (uri, { orderId }) => ({
    contents: [{ uri: uri.href, text: await renderOrder(orderId as string) }],
  }),
);

The template’s handler receives the resolved variables as its second argument.

The ui://views/ namespace is reserved for the view resources Skybridge registers for you. Registering a resource under it throws.

Completions

A dynamic resource can help the host discover and complete its URIs. The ResourceTemplate constructor takes two callbacks:

server.ts

new ResourceTemplate("orders://{orderId}", {
  // Enumerate concrete resources the template produces.
  list: async () => ({
    resources: (await recentOrders()).map((id) => ({
      name: id,
      uri: `orders://${id}`,
    })),
  }),
  // Autocomplete a variable as the user types it.
  complete: {
    orderId: async (value) => (await matchOrderIds(value)).slice(0, 20),
  },
});

list is required: pass undefined to opt out, so a template is never accidentally unlistable. complete is optional, one callback per template variable, returning the candidate values for what the user has typed so far.

Register Prompts

The third primitive: reusable prompts users can invoke.

Go Further