embr-foundry-tool-sample-dotnet

A minimal .NET / ASP.NET Core tool server that exposes the same two tools through two Foundry-consumable surfaces:

• OpenAPI (custom skill) at /api/* + spec at /openapi/v1.json.
• MCP (Model Context Protocol) streamable-HTTP at /mcp.

Same code path, two doors. Lets you compare the two integration paths from a single deployment.

This is the .NET sibling of embr-foundry-tool-sample-python.

What's in the box

• ASP.NET Core minimal-API web app on net10.0.
• Two tools: getWeather and getTime — pure static methods, decorated with [Description] for both surfaces.
• OpenAPI spec generated by Microsoft.AspNetCore.OpenApi with an x-api-key security scheme declared (Foundry's custom-OpenAPI tool import rejects anonymous specs).
• MCP server via the official ModelContextProtocol.AspNetCore SDK, mounted at /mcp with stateless HTTP transport. Tools are auto-discovered via [McpServerTool] attributes.

Layout

app/
  Program.cs    # endpoint mapping, OpenAPI transformer, MCP wiring
  Tools.cs      # core tool implementations + DTOs
  McpTools.cs   # [McpServerToolType] wrappers over Tools.* for the MCP server
embr.yaml       # Embr deploy config (platform: dotnet)
.env.example    # optional TOOL_API_KEY for runtime auth

Surfaces

Path	Purpose
/health	Liveness probe
/	Index — points at the two surfaces
/api/weather?location=...	OpenAPI tool (returns WeatherResponse)
/api/time?timezone=...	OpenAPI tool (returns TimeResponse)
/openapi/v1.json	OpenAPI 3.1 spec — feed this to Foundry's "custom OpenAPI tool"
/mcp	MCP streamable-HTTP — register as a remote MCP tool in Foundry

Auth

The OpenAPI spec declares an x-api-key header security scheme (Foundry requires at least one auth scheme on imported tools). At runtime:

• If TOOL_API_KEY is unset, requests are accepted without a header. This is the easy mode for the Foundry import flow and local development.
• If TOOL_API_KEY is set, /api/* requests must include x-api-key: <value> or get a 401.

The MCP surface does not enforce the header — Foundry's MCP connection configuration is the auth boundary there.

Run locally

cd app
dotnet run

Then:

curl http://localhost:5000/health
curl 'http://localhost:5000/api/weather?location=Seattle'
curl 'http://localhost:5000/api/time?timezone=America/New_York'
curl http://localhost:5000/openapi/v1.json | jq .

For the MCP surface, post a JSON-RPC initialize:

curl -s -X POST http://localhost:5000/mcp \
  -H 'Accept: application/json,text/event-stream' \
  -H 'Content-Type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-03-26","capabilities":{},"clientInfo":{"name":"curl","version":"1"}}}'

Deploy to Embr

gh repo create embr-foundry-tool-sample-dotnet --source=. --public --push
embr quickstart deploy <your-user>/embr-foundry-tool-sample-dotnet
# optional:
embr variables set TOOL_API_KEY <secret> -p <projectId> -e <envId> -s

Once deployed, the URL Foundry needs is:

• OpenAPI: https://<your-deploy>/openapi/v1.json
• MCP: https://<your-deploy>/mcp

Notes

• Tool implementations are pure (no external deps), so behavior is fully identical between the OpenAPI route and the MCP tool call.
• app.MapMcp("/mcp") handles both /mcp and /mcp/ cleanly — no manual trailing-slash workaround needed (unlike the Python FastMCP variant).