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.NET: Implement tool events > function call events for AG-UI support #4824

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77 changes: 77 additions & 0 deletions dotnet/src/Microsoft.Agents.AI.GitHub.Copilot/GitHubCopilotAgent.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -185,6 +185,14 @@ protected override async IAsyncEnumerable<AgentResponseUpdate> RunCoreStreamingA
channel.Writer.TryWrite(this.ConvertToAgentResponseUpdate(usageEvent));
break;

case ToolExecutionStartEvent toolStart:
channel.Writer.TryWrite(this.ConvertToolStartToAgentResponseUpdate(toolStart));
break;

case ToolExecutionCompleteEvent toolComplete:
channel.Writer.TryWrite(this.ConvertToolCompleteToAgentResponseUpdate(toolComplete));
break;

case SessionIdleEvent idleEvent:
channel.Writer.TryWrite(this.ConvertToAgentResponseUpdate(idleEvent));
channel.Writer.TryComplete();
Expand Down Expand Up @@ -430,6 +438,75 @@ private AgentResponseUpdate ConvertToAgentResponseUpdate(SessionEvent sessionEve
};
}

internal AgentResponseUpdate ConvertToolStartToAgentResponseUpdate(ToolExecutionStartEvent toolStart)
{
IDictionary<string, object?>? arguments = null;
if (toolStart.Data?.Arguments is JsonElement jsonArgs)
{
arguments = ConvertJsonElementToArguments(jsonArgs);
}

string toolName = toolStart.Data?.McpToolName ?? toolStart.Data?.ToolName ?? string.Empty;
string callId = toolStart.Data?.ToolCallId ?? string.Empty;

FunctionCallContent functionCallContent = new(callId, toolName, arguments)
{
RawRepresentation = toolStart
};

return new AgentResponseUpdate(ChatRole.Assistant, [functionCallContent])
{
AgentId = this.Id,
MessageId = callId,
CreatedAt = toolStart.Timestamp
};
}

internal AgentResponseUpdate ConvertToolCompleteToAgentResponseUpdate(ToolExecutionCompleteEvent toolComplete)
{
string callId = toolComplete.Data?.ToolCallId ?? string.Empty;
object? result = toolComplete.Data?.Result?.Content
?? toolComplete.Data?.Error?.Message;

FunctionResultContent functionResultContent = new(callId, result)
{
RawRepresentation = toolComplete
};

return new AgentResponseUpdate(ChatRole.Tool, [functionResultContent])
{
AgentId = this.Id,
MessageId = callId,
CreatedAt = toolComplete.Timestamp
};
}

private static Dictionary<string, object?>? ConvertJsonElementToArguments(JsonElement element)
{
if (element.ValueKind != JsonValueKind.Object)
{
return null;
}

Dictionary<string, object?> arguments = [];
foreach (JsonProperty property in element.EnumerateObject())
{
arguments[property.Name] = property.Value.ValueKind switch
{
JsonValueKind.String => property.Value.GetString(),
JsonValueKind.True => true,
JsonValueKind.False => false,
JsonValueKind.Null => null,
JsonValueKind.Number => property.Value.TryGetInt64(out long l)
? (object?)l
: property.Value.GetDouble(),
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Copilot AI Mar 21, 2026

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ConvertJsonElementToArguments currently converts non-primitive argument values (e.g., JsonValueKind.Object/Array) using GetRawText(), which turns them into JSON strings. When these arguments are later serialized (e.g., into AG-UI ToolCallArgs events), nested objects/arrays will be double-encoded instead of remaining structured JSON. Prefer preserving structured values by returning JsonElement (e.g., property.Value.Clone()) for Object/Array (and consider how to handle Undefined), so downstream serialization emits proper JSON objects/arrays.

Suggested change
: property.Value.GetDouble(),
: property.Value.GetDouble(),
JsonValueKind.Object => property.Value.Clone(),
JsonValueKind.Array => property.Value.Clone(),
JsonValueKind.Undefined => null,

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_ => property.Value.GetRawText()
};
}

return arguments;
}

private static SessionConfig? GetSessionConfig(IList<AITool>? tools, string? instructions)
{
List<AIFunction>? mappedTools = tools is { Count: > 0 } ? tools.OfType<AIFunction>().ToList() : null;
Expand Down
234 changes: 234 additions & 0 deletions dotnet/tests/Microsoft.Agents.AI.GitHub.Copilot.UnitTests/GitHubCopilotAgentTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@

using System;
using System.Collections.Generic;
using System.Text.Json;
using System.Threading.Tasks;
using GitHub.Copilot.SDK;
using Microsoft.Extensions.AI;
Expand Down Expand Up @@ -243,4 +244,237 @@ public void ConvertToAgentResponseUpdate_AssistantMessageEvent_DoesNotEmitTextCo
Assert.Empty(result.Text);
Assert.DoesNotContain(result.Contents, c => c is TextContent);
}

[Fact]
public void ConvertToolStartToAgentResponseUpdate_WithMcpToolName_ReturnsFunctionCallContent()
{
// Arrange
CopilotClient copilotClient = new(new CopilotClientOptions { AutoStart = false });
const string AgentId = "agent-id";
var agent = new GitHubCopilotAgent(copilotClient, ownsClient: false, id: AgentId, tools: null);
var timestamp = DateTimeOffset.UtcNow;
var toolStart = new ToolExecutionStartEvent
{
Data = new ToolExecutionStartData
{
ToolCallId = "call-123",
ToolName = "fallback_tool",
McpToolName = "mcp_tool",
Arguments = JsonSerializer.SerializeToElement(new { param1 = "value1", count = 42 })
},
Timestamp = timestamp
};

// Act
AgentResponseUpdate result = agent.ConvertToolStartToAgentResponseUpdate(toolStart);

// Assert
Assert.Equal(ChatRole.Assistant, result.Role);
Assert.Equal(AgentId, result.AgentId);
Assert.Equal("call-123", result.MessageId);
Assert.Equal(timestamp, result.CreatedAt);
FunctionCallContent content = Assert.IsType<FunctionCallContent>(Assert.Single(result.Contents));
Assert.Equal("call-123", content.CallId);
Assert.Equal("mcp_tool", content.Name);
Assert.NotNull(content.Arguments);
Assert.Equal("value1", content.Arguments["param1"]);
Assert.Equal(42L, content.Arguments["count"]);
Assert.Same(toolStart, content.RawRepresentation);
}

[Fact]
public void ConvertToolStartToAgentResponseUpdate_WithToolNameFallback_UsesToolName()
{
// Arrange
CopilotClient copilotClient = new(new CopilotClientOptions { AutoStart = false });
var agent = new GitHubCopilotAgent(copilotClient, ownsClient: false, tools: null);
var toolStart = new ToolExecutionStartEvent
{
Data = new ToolExecutionStartData
{
ToolCallId = "call-456",
ToolName = "local_tool",
}
};

// Act
AgentResponseUpdate result = agent.ConvertToolStartToAgentResponseUpdate(toolStart);

// Assert
FunctionCallContent content = Assert.IsType<FunctionCallContent>(Assert.Single(result.Contents));
Assert.Equal("local_tool", content.Name);
Assert.Null(content.Arguments);
}

[Fact]
public void ConvertToolStartToAgentResponseUpdate_WithNonObjectJsonArguments_ReturnsNullArguments()
{
// Arrange
CopilotClient copilotClient = new(new CopilotClientOptions { AutoStart = false });
var agent = new GitHubCopilotAgent(copilotClient, ownsClient: false, tools: null);
var toolStart = new ToolExecutionStartEvent
{
Data = new ToolExecutionStartData
{
ToolCallId = "call-789",
ToolName = "some_tool",
Arguments = JsonSerializer.SerializeToElement("just a string")
}
};

// Act
AgentResponseUpdate result = agent.ConvertToolStartToAgentResponseUpdate(toolStart);

// Assert
FunctionCallContent content = Assert.IsType<FunctionCallContent>(Assert.Single(result.Contents));
Assert.Null(content.Arguments);
}

[Fact]
public void ConvertToolStartToAgentResponseUpdate_WithAllJsonValueKinds_ConvertsCorrectly()
{
// Arrange
CopilotClient copilotClient = new(new CopilotClientOptions { AutoStart = false });
var agent = new GitHubCopilotAgent(copilotClient, ownsClient: false, tools: null);
var toolStart = new ToolExecutionStartEvent
{
Data = new ToolExecutionStartData
{
ToolCallId = "call-kinds",
ToolName = "multi_type_tool",
Arguments = JsonSerializer.SerializeToElement(new
{
strVal = "hello",
boolTrue = true,
boolFalse = false,
nullVal = (string?)null,
intVal = 100,
floatVal = 3.14,
objVal = new { nested = "value" }
})
}
};

// Act
AgentResponseUpdate result = agent.ConvertToolStartToAgentResponseUpdate(toolStart);

// Assert
FunctionCallContent content = Assert.IsType<FunctionCallContent>(Assert.Single(result.Contents));
Assert.NotNull(content.Arguments);
Assert.Equal("hello", content.Arguments["strVal"]);
Assert.Equal(true, content.Arguments["boolTrue"]);
Assert.Equal(false, content.Arguments["boolFalse"]);
Assert.Null(content.Arguments["nullVal"]);
Assert.Equal(100L, content.Arguments["intVal"]);
Assert.Equal(3.14, (double)content.Arguments["floatVal"]!, 2);
// Non-primitive values fall back to raw JSON text
Assert.IsType<string>(content.Arguments["objVal"]);
Comment on lines +370 to +371
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Copilot AI Mar 21, 2026

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The test currently asserts objVal is a string (raw JSON text). If arguments are intended to round-trip as structured JSON through the AG-UI layer, nested object/array values should be preserved as structured types (e.g., JsonElement) rather than raw JSON strings. Consider updating this assertion to validate the intended structured representation so regressions don’t reintroduce double-encoding of nested arguments.

Suggested change
// Non-primitive values fall back to raw JSON text
Assert.IsType<string>(content.Arguments["objVal"]);
// Non-primitive values are preserved as structured JSON
var objValElement = Assert.IsType<JsonElement>(content.Arguments["objVal"]);
Assert.Equal("value", objValElement.GetProperty("nested").GetString());

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}

[Fact]
public void ConvertToolCompleteToAgentResponseUpdate_WithResult_ReturnsFunctionResultContent()
{
// Arrange
CopilotClient copilotClient = new(new CopilotClientOptions { AutoStart = false });
const string AgentId = "agent-id";
var agent = new GitHubCopilotAgent(copilotClient, ownsClient: false, id: AgentId, tools: null);
var timestamp = DateTimeOffset.UtcNow;
var toolComplete = new ToolExecutionCompleteEvent
{
Data = new ToolExecutionCompleteData
{
ToolCallId = "call-123",
Success = true,
Result = new ToolExecutionCompleteDataResult { Content = "tool output" }
},
Timestamp = timestamp
};

// Act
AgentResponseUpdate result = agent.ConvertToolCompleteToAgentResponseUpdate(toolComplete);

// Assert
Assert.Equal(ChatRole.Tool, result.Role);
Assert.Equal(AgentId, result.AgentId);
Assert.Equal("call-123", result.MessageId);
Assert.Equal(timestamp, result.CreatedAt);
FunctionResultContent content = Assert.IsType<FunctionResultContent>(Assert.Single(result.Contents));
Assert.Equal("call-123", content.CallId);
Assert.Equal("tool output", content.Result);
Assert.Same(toolComplete, content.RawRepresentation);
}

[Fact]
public void ConvertToolCompleteToAgentResponseUpdate_WithError_ReturnsErrorMessage()
{
// Arrange
CopilotClient copilotClient = new(new CopilotClientOptions { AutoStart = false });
var agent = new GitHubCopilotAgent(copilotClient, ownsClient: false, tools: null);
var toolComplete = new ToolExecutionCompleteEvent
{
Data = new ToolExecutionCompleteData
{
ToolCallId = "call-err",
Success = false,
Error = new ToolExecutionCompleteDataError { Message = "Something went wrong" }
}
};

// Act
AgentResponseUpdate result = agent.ConvertToolCompleteToAgentResponseUpdate(toolComplete);

// Assert
FunctionResultContent content = Assert.IsType<FunctionResultContent>(Assert.Single(result.Contents));
Assert.Equal("call-err", content.CallId);
Assert.Equal("Something went wrong", content.Result);
}

[Fact]
public void ConvertToolCompleteToAgentResponseUpdate_ResultTakesPrecedenceOverError()
{
// Arrange
CopilotClient copilotClient = new(new CopilotClientOptions { AutoStart = false });
var agent = new GitHubCopilotAgent(copilotClient, ownsClient: false, tools: null);
var toolComplete = new ToolExecutionCompleteEvent
{
Data = new ToolExecutionCompleteData
{
ToolCallId = "call-both",
Success = true,
Result = new ToolExecutionCompleteDataResult { Content = "actual result" },
Error = new ToolExecutionCompleteDataError { Message = "should be ignored" }
}
};

// Act
AgentResponseUpdate result = agent.ConvertToolCompleteToAgentResponseUpdate(toolComplete);

// Assert
FunctionResultContent content = Assert.IsType<FunctionResultContent>(Assert.Single(result.Contents));
Assert.Equal("actual result", content.Result);
}

[Fact]
public void ConvertToolCompleteToAgentResponseUpdate_WithNoResultOrError_ReturnsNullResult()
{
// Arrange
CopilotClient copilotClient = new(new CopilotClientOptions { AutoStart = false });
var agent = new GitHubCopilotAgent(copilotClient, ownsClient: false, tools: null);
var toolComplete = new ToolExecutionCompleteEvent
{
Data = new ToolExecutionCompleteData
{
ToolCallId = "call-empty",
Success = true
}
};

// Act
AgentResponseUpdate result = agent.ConvertToolCompleteToAgentResponseUpdate(toolComplete);

// Assert
FunctionResultContent content = Assert.IsType<FunctionResultContent>(Assert.Single(result.Contents));
Assert.Equal("call-empty", content.CallId);
Assert.Null(content.Result);
}
}
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