Error: DynamoDB parameter validation failed

Boto3’s “Parameter validation failed” usually comes from botocore before it sends the request. The message reports a missing field, unknown parameter, wrong type, or invalid length. Fix that exact field; changing IAM permissions will not repair local parameter validation.

import boto3
from botocore.exceptions import ParamValidationError

db = boto3.client("dynamodb", region_name="us-east-1")
try:
    result = db.get_item(TableName="Orders", Key={"id": {"S": "123"}})
except ParamValidationError as error:
    print(error)
    raise

Low-level clients use typed AttributeValue maps. Table resources use native Python values, such as Key={"id":"123"}. Do not pass a JSON string in place of Key, omit required TableName, or use snake_case names for service parameters such as AttributeName.

Use Python booleans for Boolean parameters and strings for low-level Number wire values. After local validation succeeds, DynamoDB can still reject schema mismatches or expressions with a service-side ValidationException. Keep those error paths separate and avoid logging sensitive item data.

See boto3 request examples and AWS documentation.