microsoft/semantic-kernel · error · FileNotFoundException

No .proto document for the specified path - {filePath} is fo

Error message

No .proto document for the specified path - {filePath} is found.

What it means

Thrown by `Kernel.CreatePluginFromGrpc` (the directory-overload) when no `grpc.proto` file exists inside the computed plugin directory. The method builds `parentDirectory/pluginDirectoryName/grpc.proto` and checks File.Exists before opening; a missing file is treated as a deployment/setup error.

Source

Thrown at dotnet/src/Functions/Functions.Grpc/Extensions/GrpcKernelExtensions.cs:107

    /// <param name="executionParameters">Optional gRPC function execution parameters.</param>
    /// <returns>A list of all the prompt functions representing the plugin.</returns>
    public static KernelPlugin CreatePluginFromGrpcDirectory(
        this Kernel kernel,
        string parentDirectory,
        string pluginDirectoryName,
        GrpcFunctionExecutionParameters? executionParameters = null)
    {
        const string ProtoFile = "grpc.proto";

        KernelVerify.ValidPluginName(pluginDirectoryName, kernel.Plugins);

        var pluginDir = Path.Combine(parentDirectory, pluginDirectoryName);
        Verify.DirectoryExists(pluginDir);

        var filePath = Path.Combine(pluginDir, ProtoFile);
        if (!File.Exists(filePath))
        {
            throw new FileNotFoundException($"No .proto document for the specified path - {filePath} is found.");
        }

        if (kernel.LoggerFactory.CreateLogger(typeof(GrpcKernelExtensions)) is ILogger logger &&
            logger.IsEnabled(LogLevel.Trace))
        {
            logger.LogTrace("Registering gRPC functions from {0} .proto document", filePath);
        }

        using var stream = File.OpenRead(filePath);

        return kernel.CreatePluginFromGrpc(stream, pluginDirectoryName, executionParameters);
    }

    /// <summary>
    /// Imports gRPC document from a file.
    /// </summary>
    /// <param name="kernel">The <see cref="Kernel"/> containing services, plugins, and other state for use throughout the operation.</param>
    /// <param name="filePath">File path to .proto document.</param>

View on GitHub (pinned to c028a0c7dc)

Solutions

1. Confirm the directory contains a file named exactly `grpc.proto`.
2. Check the resolved `pluginDir` path (parentDirectory + pluginDirectoryName) is what you expect.
3. Ensure the .proto file is marked 'Copy to Output Directory' in your .csproj.

Example fix

// before
kernel.CreatePluginFromGrpc(@"./plugins", "math");
// after
// verify ./plugins/math/grpc.proto exists, then:
kernel.CreatePluginFromGrpc(@"./plugins", "math");

var protoPath = Path.Combine(parentDirectory, pluginDirectoryName, "grpc.proto");
if (!File.Exists(protoPath))
    throw new InvalidOperationException($"Expected .proto at {protoPath}");
kernel.CreatePluginFromGrpc(parentDirectory, pluginDirectoryName);

When it happens

Trigger: Calling `kernel.CreatePluginFromGrpc(parentDir, pluginName)` where the plugin folder lacks a `grpc.proto`, or the folder name is misspelled so the resolved path is wrong.

Common situations: Wrong working directory / relative path; plugin assets not copied to the output directory; renamed plugin folder; case-sensitive filesystem mismatch.

Related errors

• ApiManifest file not found: {filePath}
• Configuration not found, please setup the notebooks first us
• Function {targetFunction} not found in plugin {this.Name}
• No address provided for the '{operation.Name}' gRPC operatio
• The address '{address}' for the '{operation.Name}' gRPC oper

AI-assisted analysis of microsoft/semantic-kernel@c028a0c7dc (2026-08-13). Data as JSON: /api/errors/63ac084ae27efbf6. Report an issue: GitHub.