3cc4863fc1Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: Stephen Toub <stoub@microsoft.com> Co-authored-by: stephentoub <2642209+stephentoub@users.noreply.github.com>
243 lines
15 KiB
C#
243 lines
15 KiB
C#
using Microsoft.Extensions.AI;
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using Microsoft.Extensions.DependencyInjection;
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using ModelContextProtocol.Client;
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using ModelContextProtocol.Protocol;
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using System.Reflection;
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using System.Text.Json;
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namespace ModelContextProtocol.Server;
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/// <summary>
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/// Represents an invocable tool used by Model Context Protocol clients and servers.
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/// </summary>
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/// <remarks>
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/// <para>
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/// <see cref="McpServerTool"/> is an abstract base class that represents an MCP tool for use in the server (as opposed
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/// to <see cref="Tool"/>, which provides the protocol representation of a tool, and <see cref="McpClientTool"/>, which
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/// provides a client-side representation of a tool). Instances of <see cref="McpServerTool"/> can be added into a
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/// <see cref="IServiceCollection"/> to be picked up automatically when <see cref="McpServer"/> is used to create
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/// an <see cref="McpServer"/>, or added into a <see cref="McpServerPrimitiveCollection{McpServerTool}"/>.
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/// </para>
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/// <para>
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/// Most commonly, <see cref="McpServerTool"/> instances are created using the static <see cref="M:McpServerTool.Create"/> methods.
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/// These methods enable creating an <see cref="McpServerTool"/> for a method, specified via a <see cref="Delegate"/> or
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/// <see cref="MethodInfo"/>, and are what are used implicitly by WithToolsFromAssembly and WithTools. The <see cref="M:McpServerTool.Create"/> methods
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/// create <see cref="McpServerTool"/> instances capable of working with a large variety of .NET method signatures, automatically handling
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/// how parameters are marshaled into the method from the JSON received from the MCP client, and how the return value is marshaled back
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/// into the <see cref="CallToolResult"/> that's then serialized and sent back to the client.
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/// </para>
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/// <para>
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/// By default, parameters are sourced from the <see cref="CallToolRequestParams.Arguments"/> dictionary, which is a collection
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/// of key/value pairs, and are represented in the JSON schema for the function, as exposed in the returned <see cref="McpServerTool"/>'s
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/// <see cref="ProtocolTool"/>'s <see cref="Tool.InputSchema"/>. Those parameters are deserialized from the
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/// <see cref="JsonElement"/> values in that collection. There are a few exceptions to this:
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/// <list type="bullet">
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/// <item>
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/// <description>
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/// <see cref="CancellationToken"/> parameters are automatically bound to a <see cref="CancellationToken"/> provided by the
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/// <see cref="McpServer"/> and that respects any <see cref="CancelledNotificationParams"/>s sent by the client for this operation's
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/// <see cref="RequestId"/>. The parameter is not included in the generated JSON schema.
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/// </description>
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/// </item>
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/// <item>
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/// <description>
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/// <see cref="IServiceProvider"/> parameters are bound from the <see cref="RequestContext{CallToolRequestParams}"/> for this request,
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/// and are not included in the JSON schema.
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/// </description>
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/// </item>
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/// <item>
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/// <description>
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/// <see cref="McpServer"/> parameters are not included in the JSON schema and are bound directly to the <see cref="McpServer"/>
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/// instance associated with this request's <see cref="RequestContext{CallToolRequestParams}"/>. Such parameters may be used to understand
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/// what server is being used to process the request, and to interact with the client issuing the request to that server.
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/// </description>
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/// </item>
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/// <item>
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/// <description>
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/// <see cref="IProgress{ProgressNotificationValue}"/> parameters accepting <see cref="ProgressNotificationValue"/> values
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/// are not included in the JSON schema and are bound to an <see cref="IProgress{ProgressNotificationValue}"/> instance manufactured
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/// to forward progress notifications from the tool to the client. If the client included a <see cref="ProgressToken"/> in their request,
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/// progress reports issued to this instance will propagate to the client as <see cref="NotificationMethods.ProgressNotification"/> notifications with
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/// that token. If the client did not include a <see cref="ProgressToken"/>, the instance will ignore any progress reports issued to it.
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/// </description>
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/// </item>
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/// <item>
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/// <description>
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/// When the <see cref="McpServerTool"/> is constructed, it may be passed an <see cref="IServiceProvider"/> via
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/// <see cref="McpServerToolCreateOptions.Services"/>. Any parameter that can be satisfied by that <see cref="IServiceProvider"/>
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/// according to <see cref="IServiceProviderIsService"/> will not be included in the generated JSON schema and will be resolved
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/// from the <see cref="IServiceProvider"/> provided to <see cref="InvokeAsync"/> rather than from the argument collection.
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/// </description>
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/// </item>
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/// <item>
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/// <description>
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/// Any parameter attributed with <see cref="FromKeyedServicesAttribute"/> will similarly be resolved from the
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/// <see cref="IServiceProvider"/> provided to <see cref="InvokeAsync"/> rather than from the argument
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/// collection, and will not be included in the generated JSON schema.
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/// </description>
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/// </item>
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/// </list>
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/// </para>
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/// <para>
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/// All other parameters are deserialized from the <see cref="JsonElement"/>s in the <see cref="CallToolRequestParams.Arguments"/> dictionary,
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/// using the <see cref="JsonSerializerOptions"/> supplied in <see cref="McpServerToolCreateOptions.SerializerOptions"/>, or if none was provided,
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/// using <see cref="McpJsonUtilities.DefaultOptions"/>.
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/// </para>
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/// <para>
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/// In general, the data supplied via the <see cref="CallToolRequestParams.Arguments"/>'s dictionary is passed along from the caller and
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/// should thus be considered unvalidated and untrusted. To provide validated and trusted data to the invocation of the tool, consider having
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/// the tool be an instance method, referring to data stored in the instance, or using an instance or parameters resolved from the <see cref="IServiceProvider"/>
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/// to provide data to the method.
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/// </para>
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/// <para>
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/// The tool method is responsible for validating its own input arguments (e.g., checking required fields, value ranges, string lengths, or
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/// any other business rules). Data annotations such as <c>RequiredAttribute</c> and
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/// <c>MaxLengthAttribute</c> on parameter types influence the generated JSON schema exposed
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/// to clients, but they are not enforced at runtime by the SDK. Validation should be performed explicitly within the tool method.
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/// </para>
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/// <para>
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/// To signal an error (including validation failures) back to the client, either throw an <see cref="McpException"/>
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/// or return a <see cref="CallToolResult"/> with <see cref="CallToolResult.IsError"/> set to <see langword="true"/>.
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/// When a tool throws an <see cref="McpException"/>, its <see cref="Exception.Message"/> is included in the error result
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/// sent to the client. Throwing any other exception type also results in an error <see cref="CallToolResult"/>, but with
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/// a generic error message (to avoid leaking sensitive information). Alternatively, a tool can declare a return type of
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/// <see cref="CallToolResult"/> to have full control over both success and error responses.
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/// </para>
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/// <para>
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/// It is important to provide clear <see cref="System.ComponentModel.DescriptionAttribute"/> values on tool methods and their parameters.
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/// These descriptions are surfaced to AI models and help them determine when and how to use the tool, what values to pass for each parameter,
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/// and what constraints the parameters have. Well-written descriptions reduce incorrect tool invocations and improve the quality of
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/// model interactions.
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/// </para>
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/// <para>
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/// Return values from a method are used to create the <see cref="CallToolResult"/> that is sent back to the client:
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/// </para>
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/// <list type="table">
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/// <item>
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/// <term><see langword="null"/></term>
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/// <description>Returns an empty <see cref="CallToolResult.Content"/> list.</description>
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/// </item>
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/// <item>
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/// <term><see cref="AIContent"/></term>
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/// <description>Converted to a single <see cref="ContentBlock"/> object using <see cref="AIContentExtensions.ToContentBlock(AIContent, JsonSerializerOptions)"/>.</description>
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/// </item>
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/// <item>
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/// <term><see cref="string"/></term>
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/// <description>Converted to a single <see cref="TextContentBlock"/> object with its text set to the string value.</description>
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/// </item>
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/// <item>
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/// <term><see cref="ContentBlock"/></term>
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/// <description>Returned as a single-item <see cref="ContentBlock"/> list.</description>
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/// </item>
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/// <item>
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/// <term><see cref="IEnumerable{AIContent}"/> of <see cref="AIContent"/></term>
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/// <description>Each <see cref="AIContent"/> is converted to a <see cref="ContentBlock"/> object using <see cref="AIContentExtensions.ToContentBlock(AIContent, JsonSerializerOptions)"/>.</description>
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/// </item>
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/// <item>
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/// <term><see cref="IEnumerable{ContentBlock}"/> of <see cref="ContentBlock"/></term>
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/// <description>Returned as the <see cref="ContentBlock"/> list.</description>
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/// </item>
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/// <item>
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/// <term><see cref="CallToolResult"/></term>
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/// <description>Returned directly without modification.</description>
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/// </item>
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/// <item>
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/// <term>Other types</term>
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/// <description>Serialized to JSON and returned as a single <see cref="ContentBlock"/> object with <see cref="ContentBlock.Type"/> set to "text".</description>
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/// </item>
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/// </list>
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/// </remarks>
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public abstract class McpServerTool : IMcpServerPrimitive
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{
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/// <summary>Initializes a new instance of the <see cref="McpServerTool"/> class.</summary>
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protected McpServerTool()
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{
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}
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/// <summary>Gets the protocol <see cref="Tool"/> type for this instance.</summary>
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public abstract Tool ProtocolTool { get; }
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/// <summary>
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/// Gets the metadata for this tool instance.
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/// </summary>
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/// <remarks>
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/// Contains attributes from the associated MethodInfo and declaring class (if any),
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/// with class-level attributes appearing before method-level attributes.
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/// </remarks>
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public abstract IReadOnlyList<object> Metadata { get; }
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/// <summary>Invokes the <see cref="McpServerTool"/>.</summary>
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/// <param name="request">The request information resulting in the invocation of this tool.</param>
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/// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
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/// <returns>The call response from invoking the tool.</returns>
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/// <exception cref="ArgumentNullException"><paramref name="request"/> is <see langword="null"/>.</exception>
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public abstract ValueTask<CallToolResult> InvokeAsync(
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RequestContext<CallToolRequestParams> request,
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CancellationToken cancellationToken = default);
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/// <summary>
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/// Creates an <see cref="McpServerTool"/> instance for a method, specified via a <see cref="Delegate"/> instance.
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/// </summary>
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/// <param name="method">The method to be represented via the created <see cref="McpServerTool"/>.</param>
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/// <param name="options">Optional options used in the creation of the <see cref="McpServerTool"/> to control its behavior.</param>
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/// <returns>The created <see cref="McpServerTool"/> for invoking <paramref name="method"/>.</returns>
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/// <exception cref="ArgumentNullException"><paramref name="method"/> is <see langword="null"/>.</exception>
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public static McpServerTool Create(
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Delegate method,
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McpServerToolCreateOptions? options = null) =>
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AIFunctionMcpServerTool.Create(method, options);
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/// <summary>
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/// Creates an <see cref="McpServerTool"/> instance for a method, specified via a <see cref="MethodInfo"/> instance.
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/// </summary>
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/// <param name="method">The method to be represented via the created <see cref="McpServerTool"/>.</param>
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/// <param name="target">The instance if <paramref name="method"/> is an instance method; otherwise, <see langword="null"/>.</param>
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/// <param name="options">Optional options used in the creation of the <see cref="McpServerTool"/> to control its behavior.</param>
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/// <returns>The created <see cref="McpServerTool"/> for invoking <paramref name="method"/>.</returns>
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/// <exception cref="ArgumentNullException"><paramref name="method"/> is <see langword="null"/>.</exception>
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/// <exception cref="ArgumentException"><paramref name="method"/> is an instance method but <paramref name="target"/> is <see langword="null"/>.</exception>
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public static McpServerTool Create(
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MethodInfo method,
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object? target = null,
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McpServerToolCreateOptions? options = null) =>
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AIFunctionMcpServerTool.Create(method, target, options);
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/// <summary>
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/// Creates an <see cref="McpServerTool"/> instance for a method, specified via a <see cref="MethodInfo"/> for
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/// an instance method, along with a <see cref="Type"/> representing the type of the target object to
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/// instantiate each time the method is invoked.
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/// </summary>
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/// <param name="method">The instance method to be represented via the created <see cref="McpServerTool"/>.</param>
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/// <param name="createTargetFunc">
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/// Callback used on each function invocation to create an instance of the type on which the instance method <paramref name="method"/>
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/// will be invoked. If the returned instance is <see cref="IAsyncDisposable"/> or <see cref="IDisposable"/>, it will
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/// be disposed of after method completes its invocation.
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/// </param>
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/// <param name="options">Optional options used in the creation of the <see cref="McpServerTool"/> to control its behavior.</param>
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/// <returns>The created <see cref="McpServerTool"/> for invoking <paramref name="method"/>.</returns>
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/// <exception cref="ArgumentNullException"><paramref name="method"/> or <paramref name="createTargetFunc"/> is <see langword="null"/>.</exception>
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public static McpServerTool Create(
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MethodInfo method,
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Func<RequestContext<CallToolRequestParams>, object> createTargetFunc,
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McpServerToolCreateOptions? options = null) =>
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AIFunctionMcpServerTool.Create(method, createTargetFunc, options);
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/// <summary>Creates an <see cref="McpServerTool"/> that wraps the specified <see cref="AIFunction"/>.</summary>
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/// <param name="function">The function to wrap.</param>
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/// <param name="options">Optional options used in the creation of the <see cref="McpServerTool"/> to control its behavior.</param>
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/// <exception cref="ArgumentNullException"><paramref name="function"/> is <see langword="null"/>.</exception>
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/// <remarks>
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/// Unlike the other overloads of Create, the <see cref="McpServerTool"/> created by <see cref="Create(AIFunction, McpServerToolCreateOptions)"/>
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/// does not provide all of the special parameter handling for MCP-specific concepts, like <see cref="McpServer"/>.
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/// </remarks>
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public static McpServerTool Create(
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AIFunction function,
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McpServerToolCreateOptions? options = null) =>
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AIFunctionMcpServerTool.Create(function, options);
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/// <inheritdoc />
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public override string ToString() => ProtocolTool.Name;
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/// <inheritdoc />
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string IMcpServerPrimitive.Id => ProtocolTool.Name;
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}
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