Why should you care?

Mobile CRM apps and hospital kiosks integrate through stable REST contracts, not embedded SDK keys.

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.Api/Controllers/AiChatController.cs
[ApiController]
[Route("api/v1/ai/chat")]
public sealed class AiChatController(IChatClient chat) : ControllerBase
{
    [HttpPost]
    public async Task<ActionResult<ChatResponseDto>> Post([FromBody] ChatRequestDto req, CancellationToken ct)
    {
        var messages = req.Messages.Select(m => new ChatMessage(m.Role, m.Content));
        var response = await chat.GetResponseAsync(messages, cancellationToken: ct);
        return Ok(new ChatResponseDto(response.Text, response.Usage?.TotalTokens));
    }
}

What happened?

• AiChatController maps DTOs to ChatMessage sequences and returns token usage for billing.
• Versioned route leaves room for breaking v2 agent payloads.

Practice next

1. Define ChatRequestDto with Role/Content message list.
2. Add Swashbuckle and document 401/429 responses.
3. Validate message count and total character limits.
4. Add If-Match header for conversation session versioning.
5. Return ProblemDetails on validation failures.

Remember

Expose AI through versioned REST DTOs, not raw SDK types. Include usage metadata for AgentNest billing. Document limits and error codes in OpenAPI.

Partner ERP widget

An ISV embeds AgentNest chat in their finance dashboard via API key.

Outcome: Stable ChatRequestDto contract lets them upgrade AgentNest without UI rewrites.