Accessing Oauth enabled hosted MCP server

[ARVINDARUN1998]

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Your Question

Hey, I have been trying to access the oauth enabled FnO mcp server using package Azure.AI.Agents.Persistent, But struggling on how to pass the bearer token or how to configure the oauth. I can able to create as a tool in foundry, but not sure how to do using SDK.

Generally how to access oauth enabled hosted mcp server

Reference:
FnO MCP Server

[ryux1]

There are two separate authentication hops here: your code authenticates to Foundry, and Foundry authenticates to the remote MCP server. DefaultAzureCredential on PersistentAgentsClient covers only the first hop; it does not automatically become the bearer token sent to FnO.

If you are staying on the classic Azure.AI.Agents.Persistent API, attach the remote-server credential to the run through MCPToolResource:

var mcp = new MCPToolResource(mcpServerLabel);
mcp.UpdateHeader("Authorization", $"Bearer {fnoAccessToken}");

ToolResources resources = mcp.ToToolResources();
ThreadRun run = agentClient.Runs.CreateRun(thread, agent, resources);

The MCP tool definition still supplies the stable server_label and server_url; the MCPToolResource label must match it. Do not place the token in the agent instructions, tool description, URL, or source code. Acquire it for the FnO resource/audience with the appropriate identity, keep it out of logs, and refresh it before expiry. Microsoft’s classic sample documents UpdateHeader for this exact custom-header path:
https://learn.microsoft.com/en-us/azure/ai-foundry/agents/how-to/tools/model-context-protocol-samples?view=foundry-classic

For new Foundry Agent Service development, Microsoft now recommends a project connection/toolbox instead of injecting a shared bearer token in every run. Store the remote MCP authentication in the project connection and reference its project_connection_id; Foundry then handles credential injection and refresh. For user-specific delegated access, use OAuth identity passthrough rather than storing one user token as a shared project secret:
https://learn.microsoft.com/en-us/azure/foundry/agents/how-to/mcp-authentication

Which option FnO needs depends on its authentication contract: static/custom bearer token, Microsoft Entra audience with managed identity, or delegated user OAuth. Confirm that audience and scopes from the FnO MCP documentation first—a valid token for Foundry itself will normally be rejected by the downstream MCP server.