MCP Resources - URIs, Templates & Reading

What Are MCP Resources?

Resources are data that an MCP server exposes for reading. Each resource has a URI and can include a MIME type. Unlike tools, which execute code, resources represent data that a client can fetch, such as files, records, or MCP App HTML.

This page follows the core MCP 2025-11-25 specification. MCP Apps uses the same resource protocol and adds the ui:// URI scheme, an HTML profile MIME type, and UI metadata. See MCP 2026-07-28 for MCP Apps for the newer caching and subscription model.

Declare the Resources Capability

A server that exposes resources declares the resources capability during initialization:

{
  "capabilities": {
    "resources": {
      "subscribe": true,
      "listChanged": true
    }
  }
}

subscribe means clients can subscribe to resource updates.
listChanged means the server can notify clients when the available resource list changes.

Discover Resources with `resources/list`

The client calls resources/list to discover available resources. This operation supports opaque cursor pagination, so clients must continue while the response contains nextCursor.

{
  "method": "resources/list",
  "params": {
    "cursor": "opaque-cursor-from-the-previous-response"
  }
}

Each resource can declare:

Field	Required	Description
`uri`	Yes	Unique resource identifier.
`name`	Yes	Programmatic or human-readable resource name.
`title`	No	Human-readable display title.
`description`	No	What the resource contains.
`icons`	No	Display icons with source, MIME type, size, and theme hints.
`mimeType`	No	Content type such as `text/markdown` or `application/json`.
`size`	No	Resource size in bytes.
`annotations`	No	Audience, priority, and last-modified hints.

{
  "uri": "ui://weather/view.html",
  "name": "weather_view",
  "title": "Weather Forecast",
  "description": "Interactive weather display",
  "mimeType": "text/html;profile=mcp-app"
}

Use URIs and URI Templates

Servers can use any URI scheme they know how to read. MCP Apps reserves ui:// for View resources. Parameterized resources use URI templates. Servers list them with resources/templates/list, which also supports cursor pagination. A template such as weather://forecast/{city} describes a family of readable resource URIs without listing every possible city.

Read Resources with `resources/read`

The client calls resources/read with a resource URI. The server returns one or more content items. Text resources use text; binary resources use base64-encoded blob.

// Request
{ "method": "resources/read", "params": { "uri": "ui://weather/view.html" } }

// Response
{
  "contents": [{
    "uri": "ui://weather/view.html",
    "mimeType": "text/html;profile=mcp-app",
    "text": "<!DOCTYPE html>..."
  }]
}

Add Resource Annotations

Resources, resource templates, and resource content can carry annotations:

Annotation	Meaning
`audience`	Intended readers, `"user"`, `"assistant"`, or both.
`priority`	Relative importance from `0.0` to `1.0`.
`lastModified`	ISO 8601 modification time.

Annotations are hints. Clients decide whether to filter, rank, or display resources based on them. When the server advertises subscribe: true, clients can send resources/subscribe for a URI. The server then sends notifications/resources/updated when that resource changes. Clients stop updates with resources/unsubscribe. When the server advertises listChanged: true, it can send notifications/resources/list_changed after resources are added or removed. The client should call resources/list again instead of assuming what changed.

Deliver MCP App Views

MCP Apps requires the MIME type text/html;profile=mcp-app, exported as RESOURCE_MIME_TYPE, for HTML Views. Resource content can include _meta.ui for CSP, iframe permissions, rendering preferences, and stable sandbox origins:

{
  "uri": "ui://weather/view.html",
  "mimeType": "text/html;profile=mcp-app",
  "text": "<!DOCTYPE html>...",
  "_meta": {
    "ui": {
      "csp": { "connectDomains": ["https://api.example.com"] },
      "permissions": { "geolocation": {} }
    }
  }
}

UI-only resources may be omitted from resources/list because MCP Apps hosts primarily discover them through the calling tool’s _meta.ui.resourceUri. The resource must still exist, and the host must be able to fetch that exact URI with resources/read.

registerAppResource

Resource _meta

Configure CSP, permissions, domain, and rendering metadata.

Core MCP Resources Specification

Read the normative resource protocol, templates, subscriptions, and annotations.

Overview

App

MCP

React

Server

Styling

Types

MCP Resources - URIs, Templates & Reading

What Are MCP Resources?

Declare the Resources Capability

Discover Resources with `resources/list`

Use URIs and URI Templates

Read Resources with `resources/read`

Add Resource Annotations

Deliver MCP App Views

registerAppResource

Resource _meta

Core MCP Resources Specification

​What Are MCP Resources?

​Declare the Resources Capability

​Discover Resources with resources/list

​Use URIs and URI Templates

​Read Resources with resources/read

​Add Resource Annotations

​Subscribe to Changes

​Deliver MCP App Views

​Related

registerAppResource

Resource _meta

Core MCP Resources Specification

What Are MCP Resources?

Declare the Resources Capability

Discover Resources with `resources/list`

Use URIs and URI Templates

Read Resources with `resources/read`

Add Resource Annotations

Subscribe to Changes

Deliver MCP App Views

Related