# Resources
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<Info>**Protocol Revision**: 2025-11-25</Info>
The Model Context Protocol (MCP) provides a standardized way for servers to expose
resources to clients. Resources allow servers to share data that provides context to
language models, such as files, database schemas, or application-specific information.
Each resource is uniquely identified by a
[URI](https://datatracker.ietf.org/doc/html/rfc3986).
## User Interaction Model
Resources in MCP are designed to be **application-driven**, with host applications
determining how to incorporate context based on their needs.
For example, applications could:
* Expose resources through UI elements for explicit selection, in a tree or list view
* Allow the user to search through and filter available resources
* Implement automatic context inclusion, based on heuristics or the AI model's selection
<img src="https://mintcdn.com/mcp/uzELntid9uQ-QMAr/specification/2025-11-25/server/resource-picker.png?fit=max&auto=format&n=uzELntid9uQ-QMAr&q=85&s=bc7bc3db17d447a69809689e5888a3ab" alt="Example of resource context picker" data-og-width="174" width="174" data-og-height="181" height="181" data-path="specification/2025-11-25/server/resource-picker.png" data-optimize="true" data-opv="3" srcset="https://mintcdn.com/mcp/uzELntid9uQ-QMAr/specification/2025-11-25/server/resource-picker.png?w=280&fit=max&auto=format&n=uzELntid9uQ-QMAr&q=85&s=b093f0470ec2596ab192c4bc20eb952c 280w, https://mintcdn.com/mcp/uzELntid9uQ-QMAr/specification/2025-11-25/server/resource-picker.png?w=560&fit=max&auto=format&n=uzELntid9uQ-QMAr&q=85&s=cbcb9e1e469251fed19d7b308b6afd40 560w, https://mintcdn.com/mcp/uzELntid9uQ-QMAr/specification/2025-11-25/server/resource-picker.png?w=840&fit=max&auto=format&n=uzELntid9uQ-QMAr&q=85&s=17cb3398d551de7422f75bcdb001a1c8 840w, https://mintcdn.com/mcp/uzELntid9uQ-QMAr/specification/2025-11-25/server/resource-picker.png?w=1100&fit=max&auto=format&n=uzELntid9uQ-QMAr&q=85&s=d47124f9e59726522461b2af86ac74e7 1100w, https://mintcdn.com/mcp/uzELntid9uQ-QMAr/specification/2025-11-25/server/resource-picker.png?w=1650&fit=max&auto=format&n=uzELntid9uQ-QMAr&q=85&s=d513f8be56a7180539e89c1fee74eae9 1650w, https://mintcdn.com/mcp/uzELntid9uQ-QMAr/specification/2025-11-25/server/resource-picker.png?w=2500&fit=max&auto=format&n=uzELntid9uQ-QMAr&q=85&s=b5b34d2d84d5a34a75d5b2539e74acd8 2500w" />
However, implementations are free to expose resources through any interface pattern that
suits their needs—the protocol itself does not mandate any specific user
interaction model.
## Capabilities
Servers that support resources **MUST** declare the `resources` capability:
```json theme={null}
{
"capabilities": {
"resources": {
"subscribe": true,
"listChanged": true
}
}
}
```
The capability supports two optional features:
* `subscribe`: whether the client can subscribe to be notified of changes to individual
resources.
* `listChanged`: whether the server will emit notifications when the list of available
resources changes.
Both `subscribe` and `listChanged` are optional—servers can support neither,
either, or both:
```json theme={null}
{
"capabilities": {
"resources": {} // Neither feature supported
}
}
```
```json theme={null}
{
"capabilities": {
"resources": {
"subscribe": true // Only subscriptions supported
}
}
}
```
```json theme={null}
{
"capabilities": {
"resources": {
"listChanged": true // Only list change notifications supported
}
}
}
```
## Protocol Messages
### Listing Resources
To discover available resources, clients send a `resources/list` request. This operation
supports [pagination](/specification/2025-11-25/server/utilities/pagination).
**Request:**
```json theme={null}
{
"jsonrpc": "2.0",
"id": 1,
"method": "resources/list",
"params": {
"cursor": "optional-cursor-value"
}
}
```
**Response:**
```json theme={null}
{
"jsonrpc": "2.0",
"id": 1,
"result": {
"resources": [
{
"uri": "file:///project/src/main.rs",
"name": "main.rs",
"title": "Rust Software Application Main File",
"description": "Primary application entry point",
"mimeType": "text/x-rust",
"icons": [
{
"src": "https://example.com/rust-file-icon.png",
"mimeType": "image/png",
"sizes": ["48x48"]
}
]
}
],
"nextCursor": "next-page-cursor"
}
}
```
### Reading Resources
To retrieve resource contents, clients send a `resources/read` request:
**Request:**
```json theme={null}
{
"jsonrpc": "2.0",
"id": 2,
"method": "resources/read",
"params": {
"uri": "file:///project/src/main.rs"
}
}
```
**Response:**
```json theme={null}
{
"jsonrpc": "2.0",
"id": 2,
"result": {
"contents": [
{
"uri": "file:///project/src/main.rs",
"mimeType": "text/x-rust",
"text": "fn main() {\n println!(\"Hello world!\");\n}"
}
]
}
}
```
### Resource Templates
Resource templates allow servers to expose parameterized resources using
[URI templates](https://datatracker.ietf.org/doc/html/rfc6570). Arguments may be
auto-completed through [the completion API](/specification/2025-11-25/server/utilities/completion).
**Request:**
```json theme={null}
{
"jsonrpc": "2.0",
"id": 3,
"method": "resources/templates/list"
}
```
**Response:**
```json theme={null}
{
"jsonrpc": "2.0",
"id": 3,
"result": {
"resourceTemplates": [
{
"uriTemplate": "file:///{path}",
"name": "Project Files",
"title": "📁 Project Files",
"description": "Access files in the project directory",
"mimeType": "application/octet-stream",
"icons": [
{
"src": "https://example.com/folder-icon.png",
"mimeType": "image/png",
"sizes": ["48x48"]
}
]
}
]
}
}
```
### List Changed Notification
When the list of available resources changes, servers that declared the `listChanged`
capability **SHOULD** send a notification:
```json theme={null}
{
"jsonrpc": "2.0",
"method": "notifications/resources/list_changed"
}
```
### Subscriptions
The protocol supports optional subscriptions to resource changes. Clients can subscribe
to specific resources and receive notifications when they change:
**Subscribe Request:**
```json theme={null}
{
"jsonrpc": "2.0",
"id": 4,
"method": "resources/subscribe",
"params": {
"uri": "file:///project/src/main.rs"
}
}
```
**Update Notification:**
```json theme={null}
{
"jsonrpc": "2.0",
"method": "notifications/resources/updated",
"params": {
"uri": "file:///project/src/main.rs"
}
}
```
## Message Flow
```mermaid theme={null}
sequenceDiagram
participant Client
participant Server
Note over Client,Server: Resource Discovery
Client->>Server: resources/list
Server-->>Client: List of resources
Note over Client,Server: Resource Template Discovery
Client->>Server: resources/templates/list
Server-->>Client: List of resource templates
Note over Client,Server: Resource Access
Client->>Server: resources/read
Server-->>Client: Resource contents
Note over Client,Server: Subscriptions
Client->>Server: resources/subscribe
Server-->>Client: Subscription confirmed
Note over Client,Server: Updates
Server--)Client: notifications/resources/updated
Client->>Server: resources/read
Server-->>Client: Updated contents
```
## Data Types
### Resource
A resource definition includes:
* `uri`: Unique identifier for the resource
* `name`: The name of the resource.
* `title`: Optional human-readable name of the resource for display purposes.
* `description`: Optional description
* `mimeType`: Optional MIME type
* `size`: Optional size in bytes
### Resource Contents
Resources can contain either text or binary data:
#### Text Content
```json theme={null}
{
"uri": "file:///example.txt",
"mimeType": "text/plain",
"text": "Resource content"
}
```
#### Binary Content
```json theme={null}
{
"uri": "file:///example.png",
"mimeType": "image/png",
"blob": "base64-encoded-data"
}
```
### Annotations
Resources, resource templates and content blocks support optional annotations that provide hints to clients about how to use or display the resource:
* **`audience`**: An array indicating the intended audience(s) for this resource. Valid values are `"user"` and `"assistant"`. For example, `["user", "assistant"]` indicates content useful for both.
* **`priority`**: A number from 0.0 to 1.0 indicating the importance of this resource. A value of 1 means "most important" (effectively required), while 0 means "least important" (entirely optional).
* **`lastModified`**: An ISO 8601 formatted timestamp indicating when the resource was last modified (e.g., `"2025-01-12T15:00:58Z"`).
Example resource with annotations:
```json theme={null}
{
"uri": "file:///project/README.md",
"name": "README.md",
"title": "Project Documentation",
"mimeType": "text/markdown",
"annotations": {
"audience": ["user"],
"priority": 0.8,
"lastModified": "2025-01-12T15:00:58Z"
}
}
```
Clients can use these annotations to:
* Filter resources based on their intended audience
* Prioritize which resources to include in context
* Display modification times or sort by recency
## Common URI Schemes
The protocol defines several standard URI schemes. This list not
exhaustive—implementations are always free to use additional, custom URI schemes.
### https\://
Used to represent a resource available on the web.
Servers **SHOULD** use this scheme only when the client is able to fetch and load the
resource directly from the web on its own—that is, it doesn’t need to read the resource
via the MCP server.
For other use cases, servers **SHOULD** prefer to use another URI scheme, or define a
custom one, even if the server will itself be downloading resource contents over the
internet.
### file://
Used to identify resources that behave like a filesystem. However, the resources do not
need to map to an actual physical filesystem.
MCP servers **MAY** identify file:// resources with an
[XDG MIME type](https://specifications.freedesktop.org/shared-mime-info-spec/0.14/ar01s02.html#id-1.3.14),
like `inode/directory`, to represent non-regular files (such as directories) that don’t
otherwise have a standard MIME type.
### git://
Git version control integration.
### Custom URI Schemes
Custom URI schemes **MUST** be in accordance with [RFC3986](https://datatracker.ietf.org/doc/html/rfc3986),
taking the above guidance in to account.
## Error Handling
Servers **SHOULD** return standard JSON-RPC errors for common failure cases:
* Resource not found: `-32002`
* Internal errors: `-32603`
Example error:
```json theme={null}
{
"jsonrpc": "2.0",
"id": 5,
"error": {
"code": -32002,
"message": "Resource not found",
"data": {
"uri": "file:///nonexistent.txt"
}
}
}
```
## Security Considerations
1. Servers **MUST** validate all resource URIs
2. Access controls **SHOULD** be implemented for sensitive resources
3. Binary data **MUST** be properly encoded
4. Resource permissions **SHOULD** be checked before operations
---
> To find navigation and other pages in this documentation, fetch the llms.txt file at: https://modelcontextprotocol.io/llms.txt
