microsoft/semantic-kernel · error · ArgumentException

The option key '{key}' is required for a Bedrock function pa

Error message

The option key '{key}' is required for a Bedrock function parameter.

What it means

Thrown by GetRequiredValue when a Bedrock function parameter dictionary is missing one of the required string keys ('name', 'type', 'description', 'required') or the value is present but not a string. The message includes the missing key name so the caller knows exactly which field is deficient. Each of the four fields is mandatory for Bedrock ParameterDetail.

Source

Thrown at dotnet/src/Agents/Bedrock/Extensions/BedrockAgentToolDefinitionExtensions.cs:49

                parameterSpec.Add(name, new Amazon.BedrockAgent.Model.ParameterDetail
                {
                    Description = description,
                    Required = isRequired,
                    Type = new Amazon.BedrockAgent.Type(type),
                });
            }
        }

        return parameterSpec;
    }

    #region private
    private static string GetRequiredValue(this Dictionary<object, object> parameter, string key)
    {
        return parameter.TryGetValue(key, out var requiredValue) && requiredValue is string requiredString
            ? requiredString
            : throw new ArgumentException($"The option key '{key}' is required for a Bedrock function parameter.");
    }
    #endregion
}

View on GitHub (pinned to c028a0c7dc)

Solutions

1. Ensure every parameter dictionary includes all four keys: 'name', 'type', 'description', 'required', each with a non-null string value.
2. For 'required', pass the string "true" or "false" (case-insensitive), not a boolean.
3. Add a validation helper that checks all four keys exist and are strings before calling CreateParameterDetails.
4. If loading from JSON, validate the schema rejects missing/null required fields.

Example fix

// before
new Dictionary<object,object> { ["name"]="foo", ["type"]="string", ["description"]="d" } // missing 'required'

// after
new Dictionary<object,object> { ["name"]="foo", ["type"]="string", ["description"]="d", ["required"]="true" }

static readonly string[] RequiredKeys = { "name", "type", "description", "required" };
foreach (var p in parameters.Cast<Dictionary<object, object>>())
{
    foreach (var key in RequiredKeys)
        if (!p.TryGetValue(key, out var v) || v is not string || string.IsNullOrEmpty((string)v))
            throw new InvalidOperationException($"Missing or non-string key '{key}' in tool parameter.");
}

static bool HasAllRequiredBedrockKeys(Dictionary<object, object> p) =>
    new[] { "name", "type", "description", "required" }.All(k =>
        p.TryGetValue(k, out var v) && v is string s && !string.IsNullOrEmpty(s));

try { var details = def.CreateParameterDetails(); }
catch (ArgumentException ex) when (ex.Message.Contains("is required for a Bedrock function parameter"))
{
    logger.LogError("Tool parameter missing a required key. Ensure name/type/description/required (all strings).");
    throw;
}

When it happens

Trigger: Registering a tool parameter dictionary that omits one of the required keys (e.g., no 'required' key), or provides a non-string value for one of them (e.g., a boolean true instead of the string "true", or an integer for 'type').

Common situations: Typo in a key name (e.g., 'require' instead of 'required'); passing a C# bool for 'required' instead of the string "true"/"false"; omitting 'description'; deserialization that dropped a null for a required field.

Related errors

• Invalid parameter type for function {agentToolDefinition.Id}
• Unsupported parameter type: {typeString}
• Message role must be either Assistant or User.
• No function results were returned.
• runtimeClient

AI-assisted analysis of microsoft/semantic-kernel@c028a0c7dc (2026-08-13). Data as JSON: /api/errors/18d263cc828313c2. Report an issue: GitHub.