> ## Documentation Index
> Fetch the complete documentation index at: https://sunpeak.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.
# MCP Resources — URIs, MIME Types & Reading
> How MCP resources work: discovery via resources/list, URI schemes, MIME types, reading via resources/read, and how MCP Apps uses resources for UI delivery.
## What Are MCP Resources?
Resources are data that an [MCP server](/docs/mcp-apps/mcp/overview) exposes for reading. Each resource is identified by a URI and has a MIME type. Unlike [tools](/docs/mcp-apps/mcp/tools) (which execute actions), resources represent data that can be fetched — files, structured data, or (in MCP Apps) interactive HTML UIs.
## Discovery (`resources/list`)
The host calls `resources/list` to discover available resources. Each resource declares:
| Field | Description |
| ------------- | -------------------------------------------------------- |
| `uri` | Unique identifier (e.g., `"ui://weather/view.html"`) |
| `name` | Human-readable name |
| `description` | What the resource contains |
| `mimeType` | Content type (e.g., `"text/html"`, `"application/json"`) |
```json theme={null}
{
"uri": "ui://weather/view.html",
"name": "Weather View",
"description": "Interactive weather display",
"mimeType": "text/html;profile=mcp-app"
}
```
## URIs
Resources are identified by URIs. Servers can use any URI scheme. MCP Apps uses the `ui://` scheme to identify UI resources that should be rendered in iframes.
## MIME Types
Each resource declares its content type via `mimeType`. MCP Apps uses the MIME type `text/html;profile=mcp-app` (exported as `RESOURCE_MIME_TYPE`) to identify HTML resources that hosts should render as interactive Views.
## Reading (`resources/read`)
The host calls `resources/read` with a resource URI to fetch its contents. The server returns an array of content items.
```json theme={null}
// Request
{ "method": "resources/read", "params": { "uri": "ui://weather/view.html" } }
// Response
{
"contents": [{
"uri": "ui://weather/view.html",
"mimeType": "text/html;profile=mcp-app",
"text": "..."
}]
}
```
## In MCP Apps
MCP Apps extends resources with `_meta.ui` metadata on content items. This lets servers declare security policies (CSP), iframe permissions, rendering preferences, and stable sandbox origins for their UIs.
```json theme={null}
{
"uri": "ui://weather/view.html",
"mimeType": "text/html;profile=mcp-app",
"text": "...",
"_meta": {
"ui": {
"csp": { "connectDomains": ["https://api.example.com"] },
"permissions": { "geolocation": {} }
}
}
}
```
Register HTML resources on the MCP server.
CSP, permissions, domain, and rendering metadata.