Class McpServerResource

Namespace

ModelContextProtocol.Server

Assembly

ModelContextProtocol.Core.dll

Represents an invocable resource used by Model Context Protocol clients and servers.

public abstract class McpServerResource : IMcpServerPrimitive

Inheritance

object

McpServerResource

Implements

IMcpServerPrimitive

Derived

DelegatingMcpServerResource

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

Remarks

McpServerResource is an abstract base class that represents an MCP resource for use in the server (as opposed to Resource or ResourceTemplate, which provide the protocol representations of a resource). Instances of McpServerResource can be added into a IServiceCollection to be picked up automatically when McpServerFactory is used to create an IMcpServer, or added into a McpServerPrimitiveCollection<T>.

Most commonly, McpServerResource instances are created using the static McpServerResource.Create methods. These methods enable creating an McpServerResource for a method, specified via a Delegate or MethodInfo, and are what are used implicitly by WithResourcesFromAssembly and McpServerBuilderExtensions.WithResources. The McpServerResource.Create methods create McpServerResource instances capable of working with a large variety of .NET method signatures, automatically handling how parameters are marshaled into the method from the URI received from the MCP client, and how the return value is marshaled back into the ReadResourceResult that's then serialized and sent back to the client.

McpServerResource is used to represent both direct resources (e.g. "resource://example") and templated resources (e.g. "resource://example/{id}").

Read resource requests do not contain separate arguments, only a URI. However, for templated resources, portions of that URI may be considered as arguments and may be bound to parameters. Further, resource methods may accept parameters that will be bound to arguments based on their type.

• CancellationToken parameters are automatically bound to a CancellationToken provided by the IMcpServer and that respects any CancelledNotifications sent by the client for this operation's RequestId.
• IServiceProvider parameters are bound from the RequestContext<TParams> for this request.
• IMcpServer parameters are bound directly to the IMcpServer instance associated with this request's RequestContext<TParams>. Such parameters may be used to understand what server is being used to process the request, and to interact with the client issuing the request to that server.
• IProgress<T> parameters accepting ProgressNotificationValue values are bound to an IProgress<T> instance manufactured to forward progress notifications from the resource to the client. If the client included a ProgressToken in their request, progress reports issued to this instance will propagate to the client as ProgressNotification notifications with that token. If the client did not include a ProgressToken, the instance will ignore any progress reports issued to it.
• When the McpServerResource is constructed, it may be passed an IServiceProvider via Services. Any parameter that can be satisfied by that IServiceProvider according to IServiceProviderIsService will be resolved from the IServiceProvider provided to the resource invocation rather than from the argument collection.
• Any parameter attributed with FromKeyedServicesAttribute will similarly be resolved from the IServiceProvider provided to the resource invocation rather than from the argument collection.
• All other parameters are bound from the data in the URI.

Return values from a method are used to create the ReadResourceResult that is sent back to the client:

ResourceContents	Wrapped in a list containing the single ResourceContents.
Microsoft.Extensions.AI.TextContent	Converted to a list containing a single TextResourceContents.
Microsoft.Extensions.AI.DataContent	Converted to a list containing a single BlobResourceContents.
string	Converted to a list containing a single TextResourceContents.
IEnumerable<T> of ResourceContents	Returned directly as a list of ResourceContents.
IEnumerable<T> of Microsoft.Extensions.AI.AIContent	Converted to a list containing a TextResourceContents for each Microsoft.Extensions.AI.TextContent and a BlobResourceContents for each Microsoft.Extensions.AI.DataContent.
IEnumerable<T> of string	Converted to a list containing a TextResourceContents, one for each string.

Other returned types will result in an InvalidOperationException being thrown.

Constructors

McpServerResource()

Initializes a new instance of the McpServerResource class.

protected McpServerResource()

Properties

IsTemplated

Gets whether this resource is a URI template with parameters as opposed to a direct resource.

public bool IsTemplated { get; }

Property Value

bool

ProtocolResource

Gets the protocol Resource type for this instance.

public virtual Resource? ProtocolResource { get; }

Property Value

Resource

Remarks

The ProtocolResourceTemplate property represents the underlying resource template definition as defined in the Model Context Protocol specification. It contains metadata like the resource templates's URI template, name, and description.

ProtocolResourceTemplate

Gets the protocol ResourceTemplate type for this instance.

public abstract ResourceTemplate ProtocolResourceTemplate { get; }

Property Value

ResourceTemplate

Remarks

The ProtocolResourceTemplate property represents the underlying resource template definition as defined in the Model Context Protocol specification. It contains metadata like the resource templates's URI template, name, and description.

Every valid resource URI is a valid resource URI template, and thus this property always returns an instance. In contrast, the ProtocolResource property may return null if the resource template contains a parameter, in which case the resource template URI is not a valid resource URI.

Methods

Create(AIFunction, McpServerResourceCreateOptions?)

Creates an McpServerResource that wraps the specified Microsoft.Extensions.AI.AIFunction.

public static McpServerResource Create(AIFunction function, McpServerResourceCreateOptions? options = null)

Parameters

function AIFunction

The function to wrap.

options McpServerResourceCreateOptions

Optional options used in the creation of the McpServerResource to control its behavior.

Returns

McpServerResource

Remarks

Unlike the other overloads of Create, the McpServerResource created by Create(AIFunction, McpServerResourceCreateOptions?) does not provide all of the special parameter handling for MCP-specific concepts, like IMcpServer.

Exceptions

ArgumentNullException

function is null.

Create(Delegate, McpServerResourceCreateOptions?)

Creates an McpServerResource instance for a method, specified via a Delegate instance.

public static McpServerResource Create(Delegate method, McpServerResourceCreateOptions? options = null)

Parameters

method Delegate

The method to be represented via the created McpServerResource.

options McpServerResourceCreateOptions

Optional options used in the creation of the McpServerResource to control its behavior.

Returns

McpServerResource

The created McpServerResource for invoking method.

Exceptions

ArgumentNullException

method is null.

Create(MethodInfo, Func<RequestContext<ReadResourceRequestParams>, object>, McpServerResourceCreateOptions?)

Creates an McpServerResource instance for a method, specified via an MethodInfo for and instance method, along with a Type representing the type of the target object to instantiate each time the method is invoked.

public static McpServerResource Create(MethodInfo method, Func<RequestContext<ReadResourceRequestParams>, object> createTargetFunc, McpServerResourceCreateOptions? options = null)

Parameters

method MethodInfo

The instance method to be represented via the created Microsoft.Extensions.AI.AIFunction.

createTargetFunc Func<RequestContext<ReadResourceRequestParams>, object>

Callback used on each function invocation to create an instance of the type on which the instance method method will be invoked. If the returned instance is IAsyncDisposable or IDisposable, it will be disposed of after method completes its invocation.

options McpServerResourceCreateOptions

Optional options used in the creation of the McpServerResource to control its behavior.

Returns

McpServerResource

The created Microsoft.Extensions.AI.AIFunction for invoking method.

Exceptions

ArgumentNullException

method is null.

Create(MethodInfo, object?, McpServerResourceCreateOptions?)

Creates an McpServerResource instance for a method, specified via a Delegate instance.

public static McpServerResource Create(MethodInfo method, object? target = null, McpServerResourceCreateOptions? options = null)

Parameters

method MethodInfo

The method to be represented via the created McpServerResource.

target object

The instance if method is an instance method; otherwise, null.

options McpServerResourceCreateOptions

Optional options used in the creation of the McpServerResource to control its behavior.

Returns

McpServerResource

The created McpServerResource for invoking method.

Exceptions

ArgumentNullException

method is null.

ArgumentException

method is an instance method but target is null.

ReadAsync(RequestContext<ReadResourceRequestParams>, CancellationToken)

Gets the resource, rendering it with the provided request parameters and returning the resource result.

public abstract ValueTask<ReadResourceResult?> ReadAsync(RequestContext<ReadResourceRequestParams> request, CancellationToken cancellationToken = default)

Parameters

request RequestContext<ReadResourceRequestParams>

The request context containing information about the resource invocation, including any arguments passed to the resource. This object provides access to both the request parameters and the server context.

cancellationToken CancellationToken

The CancellationToken to monitor for cancellation requests. The default is None.

Returns

ValueTask<ReadResourceResult>

A ValueTask<TResult> representing the asynchronous operation, containing a ReadResourceResult with the resource content and messages. If and only if this McpServerResource doesn't match the Uri, the method returns null.

Exceptions

ArgumentNullException

request is null.

InvalidOperationException

The resource implementation returned null or an unsupported result type.

ToString()

Returns a string that represents the current object.

public override string ToString()

Returns

string

A string that represents the current object.