Problem with deserialization of Response Error property #512
Description
Bug Report
Overview
When calling tools and a tool throws an exception the Error property is not being deserialized properly.
To Reproduce
Steps to reproduce the behavior:
MCP tool throws the exception like:
// Check if the client supports elicitation
if (server.ClientCapabilities?.Elicitation == null)
{
// fail the tool call
throw new McpException("Client does not support elicitation");
}in the client error thrown in response deserialization method:
internal static T Deserialize<T>(this HttpResponseMessage response, JsonNode jNode, OpenAIClient client)
{
T result;
try
{
result = jNode.Deserialize<T>(OpenAIClient.JsonSerializationOptions); // <<<< trows exception
}
catch (Exception e)
{
Console.WriteLine($"Failed to parse {typeof(T).Name} -> {jNode.ToJsonString(DebugJsonOptions)}\n{e}");
throw;
}
if (result is BaseResponse resultResponse)
{
resultResponse.SetResponseData(response.Headers, client);
}
return result;
}Exception:
{"The JSON value could not be converted to System.String. Path: $.error | LineNumber: 0 | BytePositionInLine: 205."} Cannot get the value of a token type 'StartObject' as a string.
FIX:
/// <summary>
/// An invocation of a tool on an MCP server.
/// </summary>
public sealed class MCPToolCall : BaseResponse, IResponseItem
{...
/// <summary>
/// The error from the tool call, if any.
/// </summary>
[JsonInclude]
[JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingDefault)]
[JsonPropertyName("error")]
public JsonNode Error { get; private set; } /// <<< change prop type
}this will at the end work for (This will deserialize):
- null
- a string
- an object
- an array
No further changes required.