Resource MCP servers

Aspire resources can expose their own MCP (Model Context Protocol) servers, enabling AI coding agents to interact directly with databases, APIs, and other services. For example, a PostgreSQL resource can expose SQL query tools, allowing an agent to run queries without leaving the conversation.

How it works

When a resource is annotated with WithMcpServer() in the AppHost, Aspire discovers the MCP endpoint and makes its tools available in two ways:

• Through the Aspire MCP server — resource tools are automatically proxied alongside the built-in Aspire MCP server tools. AI agents see them in their tool list without any extra configuration.
• Through the CLI — use aspire mcp tools and aspire mcp call to discover and invoke resource tools directly from the terminal.

Add an MCP server to a resource

Use the WithMcpServer() extension method to declare that a resource hosts an MCP server:

C#

#pragma warning disable ASPIREMCP001
  
var builder = DistributedApplication.CreateBuilder(args);
  
var db = builder.AddPostgres("db")
    .AddDatabase("appdata");
  
// Expose PostgreSQL MCP tools (SQL queries, schema inspection, etc.)
db.WithPostgresMcp();
  
builder.Build().Run();

TypeScript

const builder = await createBuilder();
  
const db = await builder
    .addPostgres("db")
    .addDatabase("appdata");
  
// Expose PostgreSQL MCP tools (SQL queries, schema inspection, etc.)
await db.withPostgresMcp();
  
await builder.build().run();

Discover available tools

Use aspire mcp tools to list all MCP tools exposed by running resources:

aspire mcp tools

For machine-readable output including input schemas:

aspire mcp tools --format Json

Call a tool

Use aspire mcp call to invoke a specific tool on a resource:

aspire mcp call   --input '{"key": "value"}'

For example, to run a SQL query on a PostgreSQL resource:

aspire mcp call appdata query --input '{"sql": "SELECT * FROM users LIMIT 5"}'

Custom MCP server resources

You can add any container that implements the MCP protocol as an MCP-enabled resource. Use WithMcpServer() to tell Aspire where the MCP endpoint lives:

C#

#pragma warning disable ASPIREMCP001
  
var builder = DistributedApplication.CreateBuilder(args);
  
// Add a custom MCP server container
var myMcpServer = builder.AddContainer("my-mcp", "myregistry/my-mcp-server")
    .WithHttpEndpoint(targetPort: 8080)
    .WithMcpServer("/mcp");
  
builder.Build().Run();

TypeScript

const builder = await createBuilder();
  
// Add a custom MCP server container
const myMcpServer = await builder
    .addContainer("my-mcp", "myregistry/my-mcp-server")
    .withHttpEndpoint({ targetPort: 8080 })
    .withMcpServer("/mcp");
  
await builder.build().run();

The WithMcpServer() method accepts an optional path and endpoint name:

• WithMcpServer() — uses the default HTTP endpoint at the root path
• WithMcpServer("/mcp") — uses the default HTTP endpoint at /mcp
• WithMcpServer("/sse", endpointName: "https") — uses a named endpoint at /sse

See also

• Use AI coding agents — set up your project for AI agents
• Aspire MCP server — the built-in MCP server tools
• ASPIREMCP001 diagnostic — experimental MCP server API warning
• ASPIREPOSTGRES001 diagnostic — experimental PostgreSQL MCP warning