Usage - Phaseo Docs

Prepare the runtime

The Agent SDK package is not yet on NuGet. Follow the source installation instructions.

Quickstart

using PhaseoAgentSdk;

var agent = AgentSdk.CreateAgent(new AgentDefinition
{
    Id = "quickstart-agent",
    Model = "openai/gpt-5.4-nano",
    Instructions = "Answer concisely and helpfully."
});

var result = await agent.Run(new RunOptions
{
    Input = "Give me one fun fact about cURL.",
    Client = AgentSdk.CreateGatewayAgentClient(),
});

Console.WriteLine(result.Output);

What it ships

AgentSdk.CreateAgent(...)
AgentSdk.DefineTool(...)
AgentSdk.CreateGatewayAgentClient(...)
a bounded tool loop over the Phaseo responses API

Advanced runtime

C# supports validation and approval delegates, HITL and manual tools, progress, recoverable errors, replayable async enumerables, stop helpers, dynamic turns, persisted NextTurnParams, normalized usage/cost, and IStateAccessor.

Streaming and cancellation

Agent.Stream(...) and Agent.ContinueStream(...) use IAsyncEnumerable over the gateway’s Responses SSE stream. Consume TextStream() or FullStream(), and call Cancel() to cancel the linked request token. Completed steps retain request IDs, provider metadata, finish reasons, warnings, usage, and cost.

Last modified on July 26, 2026