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.NET: Delegate MCP ContentBlock to AIContent conversion to the MCP SDK (#5903)

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* Add sample for invoking Foundry Toolbox tools from declarative workflows

* Addressed initial PR comments.

* Delegate MCP ContentBlock to AIContent conversion to the MCP SDK

* Addressed additional properties metadata in the conversion fallback.
This commit is contained in:
Peter Ibekwe
2026-05-18 13:39:56 -07:00
committed by GitHub
Unverified
parent aad20c2b33
commit 3ebbdb01b4
2 changed files with 222 additions and 112 deletions
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dotnet/src/Microsoft.Agents.AI.Workflows.Declarative.Mcp/DefaultMcpToolHandler.cs
+31 -28
View File
@@ -12,6 +12,7 @@ using System.Threading;
using System.Threading.Tasks;
using Microsoft.Extensions.AI;
using Microsoft.Shared.Diagnostics;
using ModelContextProtocol;
using ModelContextProtocol.Client;
using ModelContextProtocol.Protocol;
@@ -27,6 +28,8 @@ namespace Microsoft.Agents.AI.Workflows.Declarative.Mcp;
/// </remarks>
public sealed class DefaultMcpToolHandler : IMcpToolHandler, IAsyncDisposable
{
private const string FilenameAdditionalPropertyName = "filename";
/// <summary>
/// Reserved <c>toolName</c> value that maps an <see cref="IMcpToolHandler.InvokeToolAsync"/> request
/// to the MCP protocol <c>tools/list</c> discovery operation.
@@ -272,46 +275,46 @@ public sealed class DefaultMcpToolHandler : IMcpToolHandler, IAsyncDisposable
internal static AIContent ConvertContentBlock(ContentBlock block)
{
return block switch
// Delegate to the MCP SDK's canonical converter. It maps every known
// ContentBlock subtype (Text/Image/Audio/EmbeddedResource/ToolUse/ToolResult)
// and sets RawRepresentation + AdditionalProperties from block.Meta.
// It intentionally returns null for ResourceLinkBlock — map that to
// UriContent here so callers always receive a usable AIContent.
return block.ToAIContent() ?? block switch
{
TextContentBlock text => new TextContent(text.Text),
ImageContentBlock image => CreateDataContent(image.Data, image.MimeType ?? "image/*"),
AudioContentBlock audio => CreateDataContent(audio.Data, audio.MimeType ?? "audio/*"),
EmbeddedResourceBlock embedded => ConvertEmbeddedResource(embedded),
_ => new TextContent(block.ToString() ?? string.Empty),
ResourceLinkBlock link => new UriContent(link.Uri, link.MimeType ?? "application/octet-stream")
{
RawRepresentation = link,
AdditionalProperties = CreateAdditionalProperties(link),
},
_ => new TextContent(block.ToString() ?? string.Empty)
{
RawRepresentation = block,
AdditionalProperties = CreateAdditionalProperties(block),
},
};
}
private static AIContent ConvertEmbeddedResource(EmbeddedResourceBlock block)
private static AdditionalPropertiesDictionary? CreateAdditionalProperties(ContentBlock block)
{
return block.Resource switch
{
TextResourceContents text => new TextContent(text.Text),
BlobResourceContents blob => CreateDataContent(blob.Blob, blob.MimeType ?? "application/octet-stream"),
_ => new TextContent(block.ToString() ?? string.Empty),
};
}
AdditionalPropertiesDictionary? properties = null;
private static DataContent CreateDataContent(ReadOnlyMemory<byte> base64Utf8Data, string mediaType)
{
if (base64Utf8Data.IsEmpty)
if (block.Meta is not null)
{
return new DataContent($"data:{mediaType};base64,", mediaType);
foreach (var property in block.Meta)
{
properties ??= new AdditionalPropertiesDictionary();
properties.Add(property.Key, property.Value);
}
}
#if NET8_0_OR_GREATER
string base64 = Encoding.UTF8.GetString(base64Utf8Data.Span);
#else
string base64 = Encoding.UTF8.GetString(base64Utf8Data.ToArray());
#endif
// If it's already a data URI, use it directly
if (base64.StartsWith("data:", StringComparison.OrdinalIgnoreCase))
if (block is ResourceLinkBlock { Name: { Length: > 0 } name })
{
return new DataContent(base64, mediaType);
properties ??= new AdditionalPropertiesDictionary();
properties.TryAdd(FilenameAdditionalPropertyName, name);
}
return new DataContent($"data:{mediaType};base64,{base64}", mediaType);
return properties;
}
private static string SerializeToolsList(IEnumerable<Tool> tools)
dotnet/tests/Microsoft.Agents.AI.Workflows.Declarative.Mcp.UnitTests/DefaultMcpToolHandlerTests.cs
+191 -84
View File
@@ -445,8 +445,9 @@ public sealed class DefaultMcpToolHandlerTests
AIContent result = DefaultMcpToolHandler.ConvertContentBlock(block);
// Assert
result.Should().BeOfType<TextContent>()
.Which.Text.Should().Be("hello world");
TextContent textContent = result.Should().BeOfType<TextContent>().Subject;
textContent.Text.Should().Be("hello world");
textContent.RawRepresentation.Should().BeSameAs(block);
}
[Fact]
@@ -462,13 +463,17 @@ public sealed class DefaultMcpToolHandlerTests
DataContent dataContent = result.Should().BeOfType<DataContent>().Subject;
dataContent.MediaType.Should().Be("image/png");
dataContent.Uri.Should().Be("data:image/png;base64,");
dataContent.Data.IsEmpty.Should().BeTrue();
dataContent.RawRepresentation.Should().BeSameAs(block);
}
[Fact]
public void ConvertContentBlock_ImageContentBlock_WithBase64Payload_ShouldReturnDataContent()
{
// Arrange
byte[] base64Bytes = Encoding.UTF8.GetBytes("iVBORw0KGgo=");
const string Base64Payload = "iVBORw0KGgo=";
byte[] base64Bytes = Encoding.UTF8.GetBytes(Base64Payload);
byte[] expectedDecoded = Convert.FromBase64String(Base64Payload);
ImageContentBlock block = new() { Data = new ReadOnlyMemory<byte>(base64Bytes), MimeType = "image/png" };
// Act
@@ -477,39 +482,9 @@ public sealed class DefaultMcpToolHandlerTests
// Assert
DataContent dataContent = result.Should().BeOfType<DataContent>().Subject;
dataContent.MediaType.Should().Be("image/png");
dataContent.Uri.Should().Be("data:image/png;base64,iVBORw0KGgo=");
}
[Fact]
public void ConvertContentBlock_ImageContentBlock_WithDataUri_ShouldReturnDataContentDirectly()
{
// Arrange
const string DataUri = "data:image/jpeg;base64,/9j/4AAQ";
byte[] dataUriBytes = Encoding.UTF8.GetBytes(DataUri);
ImageContentBlock block = new() { Data = new ReadOnlyMemory<byte>(dataUriBytes), MimeType = "image/jpeg" };
// Act
AIContent result = DefaultMcpToolHandler.ConvertContentBlock(block);
// Assert
DataContent dataContent = result.Should().BeOfType<DataContent>().Subject;
dataContent.MediaType.Should().Be("image/jpeg");
dataContent.Uri.Should().Be(DataUri);
}
[Fact]
public void ConvertContentBlock_ImageContentBlock_WithNullMimeType_ShouldDefaultToImageWildcard()
{
// Arrange
byte[] base64Bytes = Encoding.UTF8.GetBytes("iVBORw0KGgo=");
ImageContentBlock block = new() { Data = new ReadOnlyMemory<byte>(base64Bytes), MimeType = null! };
// Act
AIContent result = DefaultMcpToolHandler.ConvertContentBlock(block);
// Assert
DataContent dataContent = result.Should().BeOfType<DataContent>().Subject;
dataContent.MediaType.Should().Be("image/*");
dataContent.Data.ToArray().Should().BeEquivalentTo(expectedDecoded);
dataContent.Uri.Should().Be($"data:image/png;base64,{Base64Payload}");
dataContent.RawRepresentation.Should().BeSameAs(block);
}
[Fact]
@@ -525,13 +500,17 @@ public sealed class DefaultMcpToolHandlerTests
DataContent dataContent = result.Should().BeOfType<DataContent>().Subject;
dataContent.MediaType.Should().Be("audio/wav");
dataContent.Uri.Should().Be("data:audio/wav;base64,");
dataContent.Data.IsEmpty.Should().BeTrue();
dataContent.RawRepresentation.Should().BeSameAs(block);
}
[Fact]
public void ConvertContentBlock_AudioContentBlock_WithBase64Payload_ShouldReturnDataContent()
{
// Arrange
byte[] base64Bytes = Encoding.UTF8.GetBytes("UklGRiQA");
const string Base64Payload = "UklGRiQA";
byte[] base64Bytes = Encoding.UTF8.GetBytes(Base64Payload);
byte[] expectedDecoded = Convert.FromBase64String(Base64Payload);
AudioContentBlock block = new() { Data = new ReadOnlyMemory<byte>(base64Bytes), MimeType = "audio/wav" };
// Act
@@ -540,39 +519,9 @@ public sealed class DefaultMcpToolHandlerTests
// Assert
DataContent dataContent = result.Should().BeOfType<DataContent>().Subject;
dataContent.MediaType.Should().Be("audio/wav");
dataContent.Uri.Should().Be("data:audio/wav;base64,UklGRiQA");
}
[Fact]
public void ConvertContentBlock_AudioContentBlock_WithDataUri_ShouldReturnDataContentDirectly()
{
// Arrange
const string DataUri = "data:audio/mp3;base64,//uQxAAA";
byte[] dataUriBytes = Encoding.UTF8.GetBytes(DataUri);
AudioContentBlock block = new() { Data = new ReadOnlyMemory<byte>(dataUriBytes), MimeType = "audio/mp3" };
// Act
AIContent result = DefaultMcpToolHandler.ConvertContentBlock(block);
// Assert
DataContent dataContent = result.Should().BeOfType<DataContent>().Subject;
dataContent.MediaType.Should().Be("audio/mp3");
dataContent.Uri.Should().Be(DataUri);
}
[Fact]
public void ConvertContentBlock_AudioContentBlock_WithNullMimeType_ShouldDefaultToAudioWildcard()
{
// Arrange
byte[] base64Bytes = Encoding.UTF8.GetBytes("UklGRiQA");
AudioContentBlock block = new() { Data = new ReadOnlyMemory<byte>(base64Bytes), MimeType = null! };
// Act
AIContent result = DefaultMcpToolHandler.ConvertContentBlock(block);
// Assert
DataContent dataContent = result.Should().BeOfType<DataContent>().Subject;
dataContent.MediaType.Should().Be("audio/*");
dataContent.Data.ToArray().Should().BeEquivalentTo(expectedDecoded);
dataContent.Uri.Should().Be($"data:audio/wav;base64,{Base64Payload}");
dataContent.RawRepresentation.Should().BeSameAs(block);
}
[Fact]
@@ -593,15 +542,18 @@ public sealed class DefaultMcpToolHandlerTests
AIContent result = DefaultMcpToolHandler.ConvertContentBlock(block);
// Assert
result.Should().BeOfType<TextContent>()
.Which.Text.Should().Be("embedded text payload");
TextContent textContent = result.Should().BeOfType<TextContent>().Subject;
textContent.Text.Should().Be("embedded text payload");
textContent.RawRepresentation.Should().BeSameAs(block);
}
[Fact]
public void ConvertContentBlock_EmbeddedResourceBlock_WithBlobResource_ShouldReturnDataContent()
{
// Arrange
byte[] base64Bytes = Encoding.UTF8.GetBytes("UklGRiQA");
const string Base64Payload = "UklGRiQA";
byte[] base64Bytes = Encoding.UTF8.GetBytes(Base64Payload);
byte[] expectedDecoded = Convert.FromBase64String(Base64Payload);
EmbeddedResourceBlock block = new()
{
Resource = new BlobResourceContents
@@ -618,21 +570,65 @@ public sealed class DefaultMcpToolHandlerTests
// Assert
DataContent dataContent = result.Should().BeOfType<DataContent>().Subject;
dataContent.MediaType.Should().Be("application/zip");
dataContent.Uri.Should().Be("data:application/zip;base64,UklGRiQA");
dataContent.Data.ToArray().Should().BeEquivalentTo(expectedDecoded);
dataContent.Uri.Should().Be($"data:application/zip;base64,{Base64Payload}");
dataContent.RawRepresentation.Should().BeSameAs(block);
}
[Fact]
public void ConvertContentBlock_EmbeddedResourceBlock_WithBlobResource_NullMimeType_DefaultsToOctetStream()
public void ConvertContentBlock_ResourceLinkBlock_WithUri_ShouldReturnUriContent()
{
// Arrange
byte[] base64Bytes = Encoding.UTF8.GetBytes("UklGRiQA");
EmbeddedResourceBlock block = new()
ResourceLinkBlock block = new()
{
Resource = new BlobResourceContents
Uri = "https://example.com/resource.bin",
Name = "resource.bin",
MimeType = "application/zip",
};
// Act
AIContent result = DefaultMcpToolHandler.ConvertContentBlock(block);
// Assert
UriContent uriContent = result.Should().BeOfType<UriContent>().Subject;
uriContent.Uri.ToString().Should().Be("https://example.com/resource.bin");
uriContent.MediaType.Should().Be("application/zip");
uriContent.RawRepresentation.Should().BeSameAs(block);
}
[Fact]
public void ConvertContentBlock_ResourceLinkBlock_WithNullMimeType_ShouldDefaultToOctetStream()
{
// Arrange
ResourceLinkBlock block = new()
{
Uri = "https://example.com/resource",
Name = "resource",
MimeType = null,
};
// Act
AIContent result = DefaultMcpToolHandler.ConvertContentBlock(block);
// Assert
UriContent uriContent = result.Should().BeOfType<UriContent>().Subject;
uriContent.Uri.ToString().Should().Be("https://example.com/resource");
uriContent.MediaType.Should().Be("application/octet-stream");
}
[Fact]
public void ConvertContentBlock_ResourceLinkBlock_WithMeta_ShouldPropagateToAdditionalProperties()
{
// Arrange
ResourceLinkBlock block = new()
{
Uri = "https://example.com/resource.bin",
Name = string.Empty,
MimeType = "application/zip",
Meta = new System.Text.Json.Nodes.JsonObject
{
Blob = new ReadOnlyMemory<byte>(base64Bytes),
Uri = "resource://example.bin",
MimeType = null!,
["traceId"] = "abc-123",
["priority"] = 7,
},
};
@@ -640,9 +636,120 @@ public sealed class DefaultMcpToolHandlerTests
AIContent result = DefaultMcpToolHandler.ConvertContentBlock(block);
// Assert
DataContent dataContent = result.Should().BeOfType<DataContent>().Subject;
dataContent.MediaType.Should().Be("application/octet-stream");
dataContent.Uri.Should().Be("data:application/octet-stream;base64,UklGRiQA");
UriContent uriContent = result.Should().BeOfType<UriContent>().Subject;
uriContent.AdditionalProperties.Should().NotBeNull();
uriContent.AdditionalProperties!.Should().HaveCount(2);
uriContent.AdditionalProperties["traceId"].Should().BeSameAs(block.Meta!["traceId"]);
uriContent.AdditionalProperties["priority"].Should().BeSameAs(block.Meta["priority"]);
}
[Fact]
public void ConvertContentBlock_ResourceLinkBlock_WithName_ShouldMapNameToFilenameAdditionalProperty()
{
// Arrange
ResourceLinkBlock block = new()
{
Uri = "https://example.com/resource.bin",
Name = "resource.bin",
MimeType = "application/zip",
};
// Act
AIContent result = DefaultMcpToolHandler.ConvertContentBlock(block);
// Assert
UriContent uriContent = result.Should().BeOfType<UriContent>().Subject;
uriContent.AdditionalProperties.Should().NotBeNull();
uriContent.AdditionalProperties!["filename"].Should().Be("resource.bin");
}
[Fact]
public void ConvertContentBlock_ToolUseContentBlock_ShouldReturnFunctionCallContent()
{
// Arrange
using JsonDocument input = JsonDocument.Parse("{\"city\":\"Seattle\",\"unit\":\"celsius\"}");
ToolUseContentBlock block = new()
{
Id = "call-1",
Name = "get_weather",
Input = input.RootElement.Clone(),
};
// Act
AIContent result = DefaultMcpToolHandler.ConvertContentBlock(block);
// Assert
FunctionCallContent call = result.Should().BeOfType<FunctionCallContent>().Subject;
call.CallId.Should().Be("call-1");
call.Name.Should().Be("get_weather");
call.Arguments.Should().NotBeNull();
call.Arguments!.Should().ContainKey("city");
call.RawRepresentation.Should().BeSameAs(block);
}
[Fact]
public void ConvertContentBlock_ToolResultContentBlock_NotError_ShouldReturnFunctionResultContent()
{
// Arrange
ToolResultContentBlock block = new()
{
ToolUseId = "call-1",
Content = [new TextContentBlock { Text = "ok" }],
IsError = false,
};
// Act
AIContent result = DefaultMcpToolHandler.ConvertContentBlock(block);
// Assert
FunctionResultContent functionResult = result.Should().BeOfType<FunctionResultContent>().Subject;
functionResult.CallId.Should().Be("call-1");
functionResult.Exception.Should().BeNull();
functionResult.RawRepresentation.Should().BeSameAs(block);
}
[Fact]
public void ConvertContentBlock_ToolResultContentBlock_WithIsError_ShouldSetException()
{
// Arrange
ToolResultContentBlock block = new()
{
ToolUseId = "call-2",
Content = [new TextContentBlock { Text = "boom" }],
IsError = true,
};
// Act
AIContent result = DefaultMcpToolHandler.ConvertContentBlock(block);
// Assert
FunctionResultContent functionResult = result.Should().BeOfType<FunctionResultContent>().Subject;
functionResult.CallId.Should().Be("call-2");
functionResult.Exception.Should().NotBeNull();
functionResult.RawRepresentation.Should().BeSameAs(block);
}
[Fact]
public void ConvertContentBlock_BlockWithMeta_ShouldPropagateToAdditionalProperties()
{
// Arrange
TextContentBlock block = new()
{
Text = "hello",
Meta = new System.Text.Json.Nodes.JsonObject
{
["traceId"] = "abc-123",
["priority"] = 7,
},
};
// Act
AIContent result = DefaultMcpToolHandler.ConvertContentBlock(block);
// Assert
result.AdditionalProperties.Should().NotBeNull();
result.AdditionalProperties!.Should().ContainKey("traceId");
result.AdditionalProperties.Should().ContainKey("priority");
}
#endregion