Add Perplexity AI Sample Agent (.NET)

[Yogeshp-MSFT]

New .NET sample demonstrating Perplexity AI as the LLM provider with the Microsoft Agents SDK. Features live web search via Perplexity's Sonar models and MCP tools for Mail and Calendar.

New directory: dotnet/perplexity/sample-agent/

Key Capabilities

• Perplexity Responses API — Direct HttpClient integration
• Custom MCP client — Lightweight JSON-RPC over Streamable HTTP (McpSession.cs)
• MCP tool discovery — Via A365 Tooling SDK with ToolingManifest.json fallback
• A365 observability — OpenTelemetry + A365 tracing exporter
• Prompt-injection defenses — System prompt treats all user content as data, not commands

How It Differs from Existing Samples

Aspect	Agent Framework / SK Samples	Perplexity Sample
AI Backend	Azure OpenAI	Perplexity AI via HttpClient
Tool Integration	Agent Framework / SK plugins	Custom MCP via McpSession
Response Mode	Streaming	Request-response
Conversation	Thread/history managed	Stateless per-turn

Files

Core: Program.cs, Agent/MyAgent.cs, PerplexityClient.cs, McpSession.cs, McpToolService.cs, AspNetExtensions.cs
Telemetry: telemetry/AgentMetrics.cs, AgentOTELExtensions.cs, A365OtelWrapper.cs
Config: appsettings.json, appsettings.Development.json, appsettings.Playground.json, ToolingManifest.json
Docs: README.md, docs/design.md
Deployment: appPackage/manifest.json, PerplexitySampleAgent.sln, .csproj

Checklist

• No secrets in committed files (placeholder credentials only)
• a365.config.json / a365.generated.config.json in .gitignore
• README with setup instructions
• Design doc with architecture overview
• Teams manifest with parameterized IDs
• OpenTelemetry + A365 observability
• MIT license headers on all source files

[Copilot]

Pull request overview

Adds a new .NET Perplexity AI sample agent under dotnet/perplexity/sample-agent/, showing Perplexity (Responses API) as the LLM provider, custom MCP-based Mail/Calendar tool invocation, and OpenTelemetry/A365 observability wiring.

Changes:

• Introduces a Perplexity Responses API client (PerplexityClient) with a multi-turn tool-call loop.
• Adds a lightweight MCP JSON-RPC client (McpSession) plus a tool discovery/execution service (McpToolService).
• Adds sample app startup, configuration, Teams app package assets, and documentation (README + design doc).

Reviewed changes

Copilot reviewed 19 out of 21 changed files in this pull request and generated 32 comments.

Show a summary per file

File	Description
dotnet/perplexity/sample-agent/Program.cs	ASP.NET Core startup wiring for agent, telemetry, auth, MCP tools, and message endpoint.
dotnet/perplexity/sample-agent/Agent/MyAgent.cs	Main agent implementation: prompt, tool loading, typing/streaming response behavior.
dotnet/perplexity/sample-agent/PerplexityClient.cs	Perplexity Responses API integration and tool-call loop logic.
dotnet/perplexity/sample-agent/McpSession.cs	Minimal MCP JSON-RPC over HTTP (incl. SSE parsing).
dotnet/perplexity/sample-agent/McpToolService.cs	MCP server discovery + tool schema sanitization + tool executor dispatch.
dotnet/perplexity/sample-agent/telemetry/AgentOTELExtensions.cs	OpenTelemetry setup (resources, tracing, metrics, exporters, health/resilience defaults).
dotnet/perplexity/sample-agent/telemetry/AgentMetrics.cs	Custom ActivitySource + Meter instruments and wrapper helpers.
dotnet/perplexity/sample-agent/telemetry/A365OtelWrapper.cs	A365 observability baggage/token-cache wrapper around agent execution.
dotnet/perplexity/sample-agent/AspNetExtensions.cs	JWT token validation / auth setup helpers for the sample.
dotnet/perplexity/sample-agent/PerplexitySampleAgent.csproj	Sample project dependencies (A365 SDK packages + OTEL + resilience).
dotnet/perplexity/sample-agent/appsettings.json	Base configuration template for auth + Perplexity settings.
dotnet/perplexity/sample-agent/appsettings.Development.json	Dev overrides (token validation disabled, placeholder secrets).
dotnet/perplexity/sample-agent/appsettings.Playground.json	Playground overrides (token validation disabled, placeholder secrets).
dotnet/perplexity/sample-agent/ToolingManifest.json	MCP server fallback manifest for Mail + Calendar tools.
dotnet/perplexity/sample-agent/README.md	Setup/run documentation and sample overview.
dotnet/perplexity/sample-agent/docs/design.md	Architecture/design notes for the sample.
dotnet/perplexity/sample-agent/appPackage/manifest.json	Teams app manifest template for the sample agent.
dotnet/perplexity/sample-agent/appPackage/color.png	Teams app icon (color).
dotnet/perplexity/sample-agent/appPackage/outline.png	Teams app icon (outline).
dotnet/perplexity/sample-agent/.gitignore	Sample-local ignores (build outputs + A365 generated config).
dotnet/perplexity/PerplexitySampleAgent.sln	Solution file referencing the sample project.

[Copilot]

Pull request overview

Copilot reviewed 19 out of 21 changed files in this pull request and generated 9 comments.

[Yogeshp-MSFT]

hi @ajmfehr can you review this pr?