Agent_Step11_Middleware

Agent Middleware

This sample demonstrates how to add middleware to intercept:

• Chat client calls (global and per‑request)
• Agent runs (guardrails and PII filtering)
• Function calling (logging/override)

What This Sample Shows

1. Microsoft Foundry integration via AIProjectClient and DefaultAzureCredential
2. Chat client middleware using ChatClientBuilder.Use(...)
3. Agent run middleware (PII redaction and wording guardrails)
4. Function invocation middleware (logging and overriding a tool result)
5. Per‑request chat client middleware
6. Per‑request function pipeline with approval
7. Combining agent‑level and per‑request middleware
8. MessageAIContextProvider middleware via AIAgentBuilder.Use(...) for injecting additional context messages
9. AIContextProvider middleware via ChatClientBuilder.Use(...) for enriching messages, tools, and instructions at the chat client level

Function Invocation Middleware

Not all agents support function invocation middleware.

Attempting to use function middleware on agents that do not wrap a ChatClientAgent or derives from it will throw an InvalidOperationException.

Note: Function invocation middleware applies to tools registered on the agent. This includes tools passed to the ChatClientAgent constructor, passed to AsAIAgent, configured through ChatClientAgentOptions.ChatOptions.Tools, or supplied for an individual run. These tools are passed through ChatOptions.Tools. Functions added directly to FunctionInvokingChatClient.AdditionalTools bypass this middleware entirely, so don't rely on the middleware to enforce checks for those functions.

Prerequisites

1. Environment variables:
   • FOUNDRY_PROJECT_ENDPOINT: Your Foundry project endpoint
   • FOUNDRY_MODEL: Model name (optional; defaults to gpt-5.4-mini)
2. Sign in with Azure CLI (PowerShell):

   az login

Running the Sample

Use PowerShell:

cd dotnet/samples/02-agents/Agents/Agent_Step11_Middleware
dotnet run