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#

AppHost.cs

#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

apphost.ts

import { createBuilder } from './.modules/aspire.js';

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();

Note

WithMcpServer() and WithPostgresMcp() are experimental APIs. Suppress the ASPIREMCP001 or ASPIREPOSTGRES001 diagnostic to use them.

Discover available tools

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

Aspire CLI

aspire mcp tools

For machine-readable output including input schemas:

Aspire CLI — JSON output

aspire mcp tools --format Json

Call a tool

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

Aspire CLI

aspire mcp call <resource> <tool> --input '{"key": "value"}'

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

Aspire CLI — Query example

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#

AppHost.cs

#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

apphost.ts

import { createBuilder } from './.modules/aspire.js';

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