AWS JSON

aws.protocols#awsJson1_1 and aws.protocols#awsJson1_0 are AWS JSON-RPC protocols. NSmithy generates typed clients for both through AwsJson11Protocol and AwsJson10Protocol. Status: Early preview, client-only.

The currently verified slice covers X-Amz-Target, AWS JSON content types, empty input/output handling, special floating-point values, and common client-side error discriminator formats. awsJson1_0 has runtime support but no separate conformance project yet.

See Protocol Status for current conformance numbers.

Maven Dependency

"software.amazon.smithy:smithy-aws-traits:1.71.0"

NuGet Packages

Purpose	Packages
Client	NSmithy.Client, NSmithy.Protocols.AwsJson

NSmithy.Protocols.AwsJson pulls in NSmithy.Codecs.Json (the JSON codec) transitively.

Modeling

Apply the AWS JSON protocol trait to the service:

$version: "2"

namespace example.weather

use aws.protocols#awsJson1_1

@awsJson1_1
service Weather {
    version: "2026-01-01"
    operations: [GetCity]
}

operation GetCity {
    input := {
        @required
        cityId: String
    }
    output := {
        @required
        name: String
    }
    errors: [NoSuchResource]
}

@error("client")
structure NoSuchResource {
    @required
    resourceType: String
}

On the Wire

AWS JSON is RPC-style: every call is a POST /, the operation is selected by the X-Amz-Target header, and input/output are JSON:

POST / HTTP/1.1
Host: api.example.com
Content-Type: application/x-amz-json-1.1
Accept: application/x-amz-json-1.1
X-Amz-Target: Weather.GetCity

{"cityId":"123"}

HTTP/1.1 200 OK
Content-Type: application/x-amz-json-1.1

{"name":"Seattle"}

X-Amz-Target is {Service}.{Operation} (awsJson1_0 uses the application/x-amz-json-1.0 content type). Errors are discriminated by the X-Amzn-Errortype header or a __type field in the body.

Usage

The generated client selects the declared protocol by default and is used exactly like every other NSmithy client — see Client & Server Usage for the client code. Only the @awsJson1_1 (or @awsJson1_0) trait is specific to this protocol.

AWS JSON support is client-only. NSmithy does not generate AWS JSON servers and does not yet provide AWS SDK-style endpoint resolution, credential chains, retries, or pagination helpers. Explicit SigV4 signing exists in early preview; see Authentication.