Connecting an agent

This guide covers two common agent setups:

Custom C# agent — you own the LLM orchestration and want MCP tools to be part of a larger workflow. Recommended when you need latency, auth, or retry control.
Azure AI Foundry — you want the Foundry Responses API or Agent service to handle orchestration, with the MCP server plugged in as a tool provider.

Before you start, you need:

A scoped environment client key (Query API + MCP Server at minimum). See the Overview.
The production endpoint https://mcp.query.enterspeed.com/ — the root URL, with http transport. There is no separate /sse endpoint.

Part 1 — C# agent (MCP client SDK)

Agents talk to the Enterspeed MCP server over MCP Streamable HTTP. In C#, the most direct client is the official ModelContextProtocol NuGet package — it opens the connection, negotiates the protocol, lists tools, and lets you call them. Authentication is a single x-api-key header on the transport.

The transport class is named SseClientTransport for historical reasons. Pointed at the root URL, as below, it speaks Streamable HTTP — you do not need a separate /sse endpoint, and there isn’t one.

Prerequisites

dotnet new console -n EnterspeedMcpAgent
cd EnterspeedMcpAgent
dotnet add package ModelContextProtocol

Store secrets with dotnet user-secrets (never commit them):

dotnet user-secrets init
dotnet user-secrets set "ENTERSPEED_MCP_KEY"  "environment-xxxxxxxx-..."

Program.cs

using ModelContextProtocol.Client;
using ModelContextProtocol.Protocol.Transport;

var enterspeedKey = Environment.GetEnvironmentVariable("ENTERSPEED_MCP_KEY")
    ?? throw new InvalidOperationException("ENTERSPEED_MCP_KEY not set");

var transport = new SseClientTransport(new SseClientTransportOptions
{
    Endpoint = new Uri("https://mcp.query.enterspeed.com/"),
    // The MCP server reads `x-api-key` on every request and forwards it to
    // the Enterspeed Query API, which validates scope and index restrictions.
    AdditionalHeaders = new Dictionary<string, string>
    {
        ["x-api-key"] = enterspeedKey
    }
});

await using var mcpClient = await McpClientFactory.CreateAsync(transport);

// Discover what this key can do
var tools = await mcpClient.ListToolsAsync();
foreach (var tool in tools)
{
    Console.WriteLine($"- {tool.Name}: {tool.Description}");
}

// Call a tool — here the static get_indices tool
var result = await mcpClient.CallToolAsync(
    "get_indices",
    new Dictionary<string, object?>());

Console.WriteLine(result.Content[0]);

Run it:

dotnet run

The output starts with the tools available to your key (static tools, the dynamic enterspeed_query tool, and one query_<indexName> tool per index you have access to) and then prints the result of the first tool call.

Driving it from an LLM (tool-use loop)

To turn this into an LLM-driven agent, hand the tools list to the model of your choice. The pattern is identical for every major LLM provider:

Call ListToolsAsync() once per session and cache the result.
Send the tool schemas to the LLM alongside the user prompt.
When the LLM emits a tool call, invoke mcpClient.CallToolAsync(name, args) and feed the response back in the next turn.
Repeat until the LLM produces a final answer.

For Claude specifically, see Connecting a client for a complete Messages-API example that wires this loop.

Alternative — the Anthropic Remote MCP connector

If you prefer to let Claude open the MCP connection itself via the inline mcp_servers feature of the Messages API, you can — but note that Anthropic’s spec currently only supports an Authorization: Bearer <token> header on the upstream MCP server; it does not let you set a custom header name. The Enterspeed MCP server reads x-api-key, so the inline connector does not work with a raw scoped key today. Workarounds:

Pass the key as an ?apiKey= query-string parameter on the MCP URL (supported by the server, but the key ends up in request logs — acceptable for prototyping only).
Use the explicit ModelContextProtocol client above and drive the tool-use loop yourself.

Alternative — Semantic Kernel plugin

If you use Microsoft.SemanticKernel, turn every MCP tool into a KernelFunction:

using Microsoft.SemanticKernel;
using ModelContextProtocol.Client;
using ModelContextProtocol.Protocol.Transport;

var transport = new SseClientTransport(new SseClientTransportOptions
{
    Endpoint = new Uri("https://mcp.query.enterspeed.com/"),
    AdditionalHeaders = new Dictionary<string, string>
    {
        ["x-api-key"] = enterspeedKey
    }
});

await using var mcp = await McpClientFactory.CreateAsync(transport);

var kernel = Kernel.CreateBuilder()
    .AddOpenAIChatCompletion("gpt-4o", azureOpenAiKey)
    .Build();

var tools = await mcp.ListToolsAsync();
kernel.Plugins.AddFromFunctions(
    "enterspeedQuery",
    tools.Select(t => t.AsKernelFunction()));

var answer = await kernel.InvokePromptAsync(
    "List the Enterspeed indices. Then describe the first one.");
Console.WriteLine(answer.GetValue<string>());

Part 2 — Azure AI Foundry (step-by-step)

Azure AI Foundry’s Responses API and Agent service can attach an MCP server as a tool provider. The flow is: your code → Foundry (with mcp_servers in the request) → MCP server → Query API.

Entra ID required for MCP on Foundry. Foundry’s MCP tool support routes through the Agent service orchestration layer, which requires Microsoft Entra ID authentication (service principal or user identity). A plain Foundry API key is not accepted for MCP-enabled requests. If you need a “simple API key” façade for end users, place a thin wrapper in front that holds the service principal.

Step 1 — Create an AI Foundry project

In the Azure portal, create an AI Foundry resource.
Inside it, create a project — e.g. enterspeed-mcp-demo.
Pick a region that supports the Responses API with MCP tool calling. swedencentral is EU-based and supported; eastus is the most feature-complete.
Deploy a model. gpt-4o is a good starting point; Claude models (claude-sonnet-4) are also available on swedencentral.

Step 2 — Create a service principal

az ad sp create-for-rbac \
  --name "enterspeed-mcp-agent" \
  --role "Azure AI User" \
  --scopes "/subscriptions/<sub-id>/resourceGroups/<rg-name>/providers/Microsoft.CognitiveServices/accounts/<foundry-resource>"

Save the returned appId, password, and tenant. If the subscription owner has not granted the service principal the Azure AI User role on the AI Services account, no MCP-enabled API call will succeed. This is the most common failure mode.

Step 3 — Configure secrets

dotnet user-secrets set "AZURE_TENANT_ID"     "<tenant-id>"
dotnet user-secrets set "AZURE_CLIENT_ID"     "<appId>"
dotnet user-secrets set "AZURE_CLIENT_SECRET" "<password>"
dotnet user-secrets set "FOUNDRY_ENDPOINT"    "https://<foundry>.services.ai.azure.com/api/projects/<project>"
dotnet user-secrets set "FOUNDRY_MODEL"       "gpt-4o"
dotnet user-secrets set "ENTERSPEED_MCP_KEY"  "environment-xxxxxxxx-..."

Step 4 — Call the Responses API with MCP attached

using Azure.Identity;
using Azure.Core;
using System.Net.Http.Json;
using Microsoft.Extensions.Configuration;

var config = new ConfigurationBuilder()
    .AddUserSecrets<Program>()
    .Build();

var credential = new ClientSecretCredential(
    config["AZURE_TENANT_ID"],
    config["AZURE_CLIENT_ID"],
    config["AZURE_CLIENT_SECRET"]);

var token = await credential.GetTokenAsync(
    new TokenRequestContext(new[] { "https://ai.azure.com/.default" }));

var http = new HttpClient
{
    BaseAddress = new Uri(config["FOUNDRY_ENDPOINT"]!)
};
http.DefaultRequestHeaders.Authorization =
    new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", token.Token);

var body = new
{
    model = config["FOUNDRY_MODEL"],
    input = "List the Enterspeed indices I have access to.",
    tools = new object[]
    {
        new
        {
            type         = "mcp",
            server_label = "enterspeedQuery",
            server_url   = "https://mcp.query.enterspeed.com/",
            // Foundry forwards this header to the MCP server on every call
            headers = new Dictionary<string, string>
            {
                ["x-api-key"] = config["ENTERSPEED_MCP_KEY"]!
            },
            require_approval = "never"
        }
    }
};

var response = await http.PostAsJsonAsync(
    "/openai/responses?api-version=2025-03-01-preview", body);
response.EnsureSuccessStatusCode();

Console.WriteLine(await response.Content.ReadAsStringAsync());

Step 5 — Validate end-to-end

Run this known-good smoke sequence:

“List my Enterspeed indices” — expect an index-listing tool call, then a list in the response.
“Describe index <name>” — expect a describe_index call with fields grouped by type.
A domain-specific question — expect one or more query_* tool calls and a synthesised answer.

If the model returns “I don’t have access to that tool” after step 1 succeeded, the key most likely lacks the Query API scope. The tool was listed (because MCP Server is present) but the call is rejected by the Query API.

Foundry Agent service (alternative)

Foundry also has a persistent Agent service. The MCP wiring is identical (an mcp tool with server_url and headers) but the agent persists across calls. Use it when you want a long-running conversation with the same tool set attached. The same Entra ID requirement applies.

Custom domain / enterprise note

If you are proxying the MCP server behind your own domain:

The Query API still validates the scoped key — the proxy must forward x-api-key verbatim.
The proxy must support HTTP streaming (chunked / SSE). Several AWS ALB and classic CDN configurations do not by default.
The MCP transport is Streamable HTTP over HTTP/1.1. Check your hop-by-hop limits before forcing HTTP/2.

Troubleshooting

Symptom	Likely cause	Fix
Foundry: `403 Identity (object id: ) does not have permissions for Microsoft.MachineLearningServices/workspaces/agents/action actions.`	Using a Foundry API key, or the service principal is missing the `Azure AI User` role	Switch to service principal auth and grant the role on the AI Services resource.
Foundry returns instantly with no tool calls	MCP server not reachable from Foundry, or TLS cert mismatch	Curl the MCP health endpoint from a network location similar to Foundry’s egress.
Tool list arrives but every call returns empty	`x-api-key` lost along the proxy chain	Trace the header end-to-end; the MCP server requires it on every request, not just at session start.
Agent times out on a long query	Default HTTP client timeout of 2 minutes exceeded	Paginate the prompt, or raise the timeout on your side.

Next steps

Connecting a client — VS Code, Claude Code, Claude Desktop, and the Anthropic Messages API in C#.
Overview — sample prompts and the full scope table.

Overview

Schema reference

API

Integrations

Tutorials

Best practices

CLI

MCP server

Part 1 — C# agent (MCP client SDK)

Prerequisites

Program.cs

Driving it from an LLM (tool-use loop)

Alternative — the Anthropic Remote MCP connector

Alternative — Semantic Kernel plugin

Part 2 — Azure AI Foundry (step-by-step)

Step 1 — Create an AI Foundry project

Step 2 — Create a service principal

Step 3 — Configure secrets

Step 4 — Call the Responses API with MCP attached

Step 5 — Validate end-to-end

Foundry Agent service (alternative)

Custom domain / enterprise note

Troubleshooting

Next steps

​Part 1 — C# agent (MCP client SDK)

​Prerequisites

​Program.cs

​Driving it from an LLM (tool-use loop)

​Alternative — the Anthropic Remote MCP connector

​Alternative — Semantic Kernel plugin

​Part 2 — Azure AI Foundry (step-by-step)

​Step 1 — Create an AI Foundry project

​Step 2 — Create a service principal

​Step 3 — Configure secrets

​Step 4 — Call the Responses API with MCP attached

​Step 5 — Validate end-to-end

​Foundry Agent service (alternative)

​Custom domain / enterprise note

​Troubleshooting

​Next steps

Part 1 — C# agent (MCP client SDK)

Prerequisites

Program.cs

Driving it from an LLM (tool-use loop)

Alternative — the Anthropic Remote MCP connector

Alternative — Semantic Kernel plugin

Part 2 — Azure AI Foundry (step-by-step)

Step 1 — Create an AI Foundry project

Step 2 — Create a service principal

Step 3 — Configure secrets

Step 4 — Call the Responses API with MCP attached

Step 5 — Validate end-to-end

Foundry Agent service (alternative)

Custom domain / enterprise note

Troubleshooting

Next steps