Why should you care?

Roadmaps include cross-agent delegation and federated memory; stable interfaces today prevent rewrites when models or protocols change tomorrow.

See it live — copy this example

Paste into an ASP.NET Core 8+ / AgentNest project, then run with dotnet run (set your API keys in user-secrets).

// AgentNest.Contracts/IAgentCapability.cs
public interface IAgentCapability
{
    string Name { get; }
    string Version { get; }
    Task<AgentResult> ExecuteAsync(AgentRequest request, CancellationToken ct);
}

public sealed record AgentRequest(string TenantId, string Intent, IReadOnlyDictionary<string, string> Args);

What happened?

• Versioned IAgentCapability lets AgentNest register v1 and v2 hospital agents side by side.
• Controllers depend on the interface, not a specific model prompt.

Practice next

1. Define AgentRequest/AgentResult records shared across agent projects.
2. Tag each agent with Name and SemVer Version in DI registration.
3. Build a contract test that runs golden intents against ExecuteAsync.
4. Add CapabilityMetadata with SupportedIntents[] for discovery endpoints.
5. Route 10% traffic to Version 2 via feature flags.

Remember

Versioned agent interfaces insulate AgentNest from model churn. Golden intent tests catch regressions before tenant rollout. Human approval remains mandatory for high-risk domains.

Agent upgrade window

New model families arrive mid-contract; tenants refuse downtime.

Outcome: IAgentCapability v2 rolls out behind flags while v1 serves ERP close week.