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:

TypeScript
C#

import { 
function createBuilder(): IDistributedApplicationBuilder
Creates a new distributed application builder
createBuilder } from './.aspire/modules/aspire.mjs';

const 
const builder: IDistributedApplicationBuilder
builder = await 
function createBuilder(): IDistributedApplicationBuilder
Creates a new distributed application builder
createBuilder();

const 
const db: PostgresDatabaseResource
db = await 
const builder: IDistributedApplicationBuilder
builder
  .
IDistributedApplicationBuilder.addPostgres(name: string, options?: {
    userName?: string | ParameterResource;
    password?: string | ParameterResource;
    port?: number;
}): PostgresServerResource (+1 overload)
Adds a PostgreSQL resource to the application model. A container is used for local development.
addPostgres("db")
  .
PostgresServerResource.addDatabase(name: string, options?: {
    databaseName?: string;
} | undefined): PostgresDatabaseResource (+1 overload)
Adds a PostgreSQL database to the application model.
addDatabase("appdata");

// Expose PostgreSQL MCP tools (SQL queries, schema inspection, etc.)
await 
const db: PostgresDatabaseResource
db.
PostgresDatabaseResource.withPostgresMcp(options?: {
    configureContainer?: ((obj: PostgresMcpContainerResource) => Promise<void>) | undefined;
    containerName?: string;
} | undefined): PostgresDatabaseResource (+1 overload)
Adds a Postgres MCP server container and configures it to connect to the database represented by builder.
withPostgresMcp();

await 
const builder: IDistributedApplicationBuilder
builder.
IDistributedApplicationBuilder.build(): DistributedApplication
Builds the distributed application
build().
DistributedApplication.run(cancellationToken?: cancellationToken): void
Runs the distributed application
run();

#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();

Postgres MCP container imageCompanion · PostgreSQLDocker Hub
```
docker.io/crystaldba/postgres-mcp:0.3.0
```
Added by WithPostgresMcp()withPostgresMcp().
Source

Tags reflect the latest defaults on the microsoft/aspire main branch, and may be newer than the version pinned by the package you install.

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 <resource> <tool> --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:

TypeScript
C#

import { 
function createBuilder(): IDistributedApplicationBuilder
Creates a new distributed application builder
createBuilder } from './.aspire/modules/aspire.mjs';

const 
const builder: IDistributedApplicationBuilder
builder = await 
function createBuilder(): IDistributedApplicationBuilder
Creates a new distributed application builder
createBuilder();

// Add a custom MCP server container
const 
const myMcpServer: ContainerResource
myMcpServer = await 
const builder: IDistributedApplicationBuilder
builder
  .
IDistributedApplicationBuilder.addContainer(name: string, image: AddContainerOptions): ContainerResource
Adds a container resource to the application.
addContainer("my-mcp", { 
AddContainerOptions.image?: string | undefined
image: "myregistry/my-mcp-server", 
AddContainerOptions.tag?: string | undefined
tag: "latest" })
  .
ContainerResource.withHttpEndpoint(options?: {
    port?: number;
    targetPort?: number;
    name?: string;
    env?: string;
    isProxied?: boolean;
} | undefined): ContainerResource (+1 overload)
Adds an HTTP endpoint
withHttpEndpoint({ 
targetPort?: number | undefined
targetPort: 8080 })
  .
ContainerResource.withMcpServer(path?: string, endpointName?: string): ContainerResource (+1 overload)
Marks the resource as hosting a Model Context Protocol (MCP) server on the specified endpoint.
withMcpServer("/mcp");

await 
const builder: IDistributedApplicationBuilder
builder.
IDistributedApplicationBuilder.build(): DistributedApplication
Builds the distributed application
build().
DistributedApplication.run(cancellationToken?: cancellationToken): void
Runs the distributed application
run();

#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();

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