Add initial support for Resource Templates (#18)

* Add initial support for Resource Templates

* Make ListResourceTemplatesHandler not required

The server was throwing if this handler wasn't specified, and it should probably be optional anyway.

* Remove extra line

Co-authored-by: Stephen Toub <stoub@microsoft.com>

* Fix spaces

Co-authored-by: Stephen Toub <stoub@microsoft.com>

* Fix spaces

Co-authored-by: Stephen Toub <stoub@microsoft.com>

* Add and use a default ListResourceTemplatesHandler

If no ListResourceTemplatesHandler is specified, use a default one that returns an empty result.

* Fix spaces

* Spaces

* Add Client extensions for ListResourceTemplates

* Integration Test for Client ListResourceTemplates

* Fix comment

Co-authored-by: Stephen Toub <stoub@microsoft.com>

* Make Defaults internal

Co-authored-by: Stephen Toub <stoub@microsoft.com>

* Simplify test call

Co-authored-by: Stephen Toub <stoub@microsoft.com>

* Make delegate static

Co-authored-by: Stephen Toub <stoub@microsoft.com>

* Fix test comment

* Spaces

* Fix xml doc

Co-authored-by: Stephen Toub <stoub@microsoft.com>

* Make default handler inline

* Spaces

Co-authored-by: Stephen Halter <halter73@gmail.com>

---------

Co-authored-by: Stephen Toub <stoub@microsoft.com>
Co-authored-by: Stephen Halter <halter73@gmail.com>

src/ModelContextProtocol/Protocol/Types/Capabilities.cs

@@ -110,6 +110,12 @@ public record ResourcesCapability
     [JsonPropertyName("listChanged")]
     public bool? ListChanged { get; init; }
 
+    /// <summary>
+    /// Gets or sets the handler for list resource templates requests.
+    /// </summary>
+    [JsonIgnore]
+    public Func<RequestContext<ListResourceTemplatesRequestParams>, CancellationToken, Task<ListResourceTemplatesResult>>? ListResourceTemplatesHandler { get; init; }
+
     /// <summary>
     /// Gets or sets the handler for list resources requests.
     /// </summary>

src/ModelContextProtocol/Protocol/Types/ListResourceTemplatesRequestParams.cs

@@ -0,0 +1,15 @@
+namespace ModelContextProtocol.Protocol.Types;
+
+/// <summary>
+/// Sent from the client to request a list of resource templates the server has.
+/// <see href="https://github.com/modelcontextprotocol/specification/blob/main/schema/2024-11-05/schema.json">See the schema for details</see>
+/// </summary>
+public class ListResourceTemplatesRequestParams
+{
+    /// <summary>
+    /// An opaque token representing the current pagination position.
+    /// If provided, the server should return results starting after this cursor.
+    /// </summary>
+    [System.Text.Json.Serialization.JsonPropertyName("cursor")]
+    public string? Cursor { get; init; }
+}

src/ModelContextProtocol/Protocol/Types/ListResourceTemplatesResult.cs

@@ -0,0 +1,16 @@
+using ModelContextProtocol.Protocol.Messages;
+
+namespace ModelContextProtocol.Protocol.Types;
+
+/// <summary>
+/// The server's response to a resources/templates/list request from the client.
+/// <see href="https://github.com/modelcontextprotocol/specification/blob/main/schema/2024-11-05/schema.json">See the schema for details</see>
+/// </summary>
+public class ListResourceTemplatesResult : PaginatedResult
+{
+    /// <summary>
+    /// A list of resource templates that the server offers.
+    /// </summary>
+    [System.Text.Json.Serialization.JsonPropertyName("resourceTemplates")]
+    public List<ResourceTemplate> ResourceTemplates { get; set; } = [];
+}

src/ModelContextProtocol/Protocol/Types/ResourceTemplate.cs

@@ -0,0 +1,42 @@
+using ModelContextProtocol.Protocol.Types;
+
+using System.Text.Json.Serialization;
+
+namespace ModelContextProtocol.Protocol.Types;
+
+/// <summary>
+/// Represents a known resource template that the server is capable of reading.
+/// <see href="https://github.com/modelcontextprotocol/specification/blob/main/schema/2024-11-05/schema.json">See the schema for details</see>
+/// </summary>
+public record ResourceTemplate
+{
+    /// <summary>
+    /// The URI template (according to RFC 6570) that can be used to construct resource URIs.
+    /// </summary>
+    [JsonPropertyName("uriTemplate")]
+    public required string UriTemplate { get; init; }
+
+    /// <summary>
+    /// A human-readable name for this resource template.
+    /// </summary>
+    [JsonPropertyName("name")]
+    public required string Name { get; init; }
+
+    /// <summary>
+    /// A description of what this resource template represents.
+    /// </summary>
+    [JsonPropertyName("description")]
+    public string? Description { get; init; }
+
+    /// <summary>
+    /// The MIME type of this resource template, if known.
+    /// </summary>
+    [JsonPropertyName("mimeType")]
+    public string? MimeType { get; init; }
+
+    /// <summary>
+    /// Optional annotations for the resource template.
+    /// </summary>
+    [JsonPropertyName("annotations")]
+    public Annotations? Annotations { get; init; }
+}