microsoft/semantic-kernel · error · KernelException

No '{fullTypeName}' message type is found while resolving da

Error message

No '{fullTypeName}' message type is found while resolving data contracts for the '{methodName}' method.

What it means

Thrown by CreateDataContract when no message type in `allMessageTypes` matches the requested `fullTypeName` (or the package-stripped `typeName`). The runner resolves each method's request/response message type by name against the set parsed from the .proto; a miss means the .proto references a message type it does not define or import.

Source

Thrown at dotnet/src/Functions/Functions.Grpc/Protobuf/ProtoDocumentParser.cs:91

    /// </summary>
    /// <param name="allMessageTypes">Existing ,message types declared in .proto file.</param>
    /// <param name="messageTypeName">Message type to create the data contract for.</param>
    /// <param name="package">The .proto file 'package' specifier.</param>
    /// <param name="methodName">The method to create data contract for.</param>
    /// <returns>The operation data contract.</returns>
    private GrpcOperationDataContractType CreateDataContract(IList<DescriptorProto> allMessageTypes, string messageTypeName, string package, string methodName)
    {
        var fullTypeName = messageTypeName.TrimStart('.');

        var typeName = fullTypeName;

        if (!string.IsNullOrEmpty(package))
        {
            typeName = fullTypeName.Replace($"{package}.", "");
        }

        var messageType = allMessageTypes.SingleOrDefault(mt => mt.Name == fullTypeName || mt.Name == typeName) ??
            throw new KernelException($"No '{fullTypeName}' message type is found while resolving data contracts for the '{methodName}' method.");

        var fields = this.GetDataContractFields(messageType.Fields);

        return new GrpcOperationDataContractType(fullTypeName, fields);
    }

    /// <summary>
    /// Returns data contract fields.
    /// </summary>
    /// <param name="fields">Message type fields.</param>
    /// <returns>The data contract fields.</returns>
    private List<GrpcOperationDataContractTypeFiled> GetDataContractFields(List<FieldDescriptorProto> fields)
    {
        var result = new List<GrpcOperationDataContractTypeFiled>();

        foreach (var field in fields)
        {
            var type = GetProtobufDataTypeName(field.type);

View on GitHub (pinned to c028a0c7dc)

Solutions

Confirm the message type referenced by the method exists in the same .proto (and is spelled identically).
Ensure the package prefix matches — `package.foo.Bar` must align with the package declaration.
Include imported .proto files so their message types appear in allMessageTypes.

Example fix

// before
service S { rpc M (Missing) returns (Missing); }
// after
message Missing { string id = 1; }
service S { rpc M (Missing) returns (Missing); }

Defensive patterns

Strategy: validation

Validate before calling

// Cross-check that every message type referenced by rpc methods is defined in the .proto or its imports.

Try / catch

try { /* register */ }
catch (KernelException ex) when (ex.Message.Contains("message type is found while resolving")) {
    // a referenced message type is missing from the schema
}

Prevention

Keep message definitions and service definitions in the same .proto when possible.
Update method signatures whenever you rename a message.

When it happens

Trigger: A service method whose input/output type name doesn't match any defined message — typo in the type name, missing message definition, or package-qualification mismatch.

Common situations: Refactoring message names in the .proto without updating method signatures; package declaration changed so the full type name differs; imported message types not included in the parsed descriptor set.

Related errors

AI-assisted analysis of microsoft/semantic-kernel@c028a0c7dc (2026-08-13). Data as JSON: /api/errors/1de3704f39800c53. Report an issue: GitHub.