> ## Documentation Index
> Fetch the complete documentation index at: https://docs.agenticenv.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# MCP Config

> Connect MCP servers using WithMCPConfig over stdio or streamable HTTP via env variables

Registers MCP servers through `WithMCPConfig` and `agent.MCPServers` — transport and credentials from env (`MCP_*`). Contrast with [MCP Client](/examples/mcp-client), which uses `mcpclient.NewClient` + `WithMCPClients`.

Source: [`examples/agent_with_mcp_config/`](https://github.com/agenticenv/agent-sdk-go/tree/main/examples/agent_with_mcp_config)

## What it demonstrates

* `MCPStdio` and `MCPStreamableHTTP` transports from env
* Tool filters, timeouts, retries per server
* Local stdio MCP using defaults in `.env.defaults` — filesystem server pointed at `mcp-filesystem-sandbox/` (sample data only, not a separate example)

## Configure MCP

**Transport** — set `MCP_TRANSPORT` to `stdio` or `streamable_http`.

**Remote (`streamable_http`):**

* `MCP_STREAMABLE_HTTP_URL` — required
* Auth: `MCP_BEARER_TOKEN`, or OAuth trio `MCP_CLIENT_ID` + `MCP_CLIENT_SECRET` + `MCP_TOKEN_URL` (OAuth wins when all three set)
* `MCP_SKIP_TLS_VERIFY=true` — dev TLS only

**Local (`stdio`):**

* `MCP_STDIO_COMMAND` and optional `MCP_STDIO_ARGS` (JSON array), `MCP_STDIO_ENV` (JSON object)

Shared optional knobs: `MCP_SERVER_NAME`, `MCP_TIMEOUT_SECONDS`, `MCP_RETRY_ATTEMPTS`, `MCP_ALLOW_TOOLS` / `MCP_BLOCK_TOOLS` (comma-separated; only one list type). See [Configuration](/examples/configuration) and committed `.env.defaults` in the repo for every variable.

## Run

From `examples/`:

```bash theme={null}
go run ./agent_with_mcp_config
go run ./agent_with_mcp_config "List tools you can call."
```

## Testing against a real HTTP MCP server

This repo does **not** start an MCP server — point `.env` at **your** server.

Example with a TypeScript streamable HTTP server on port 8123:

```bash theme={null}
# In examples/.env:
# MCP_TRANSPORT=streamable_http
# MCP_STREAMABLE_HTTP_URL=http://localhost:8123/mcp
go run ./agent_with_mcp_config
```

Quick check while the server runs: `curl -sS -o /dev/null -w "%{http_code}\n" "http://localhost:8123/mcp"`

For **stdio**, set `MCP_STDIO_COMMAND` (and args/env if needed). The SDK spawns the subprocess and speaks MCP over stdin/stdout.

## Expected output

With the default stdio filesystem MCP server and no prompt:

```
I have access to the following MCP tools: read_file, write_file, list_directory,
create_directory, and move_file. These let me interact with the local filesystem
sandbox. How can I help?
```

The exact tool list reflects what the MCP server advertises on startup. With a remote HTTP server the response depends on that server's capabilities.

## Learn more

<CardGroup cols={2}>
  <Card title="MCP" icon="plug" href="/features/mcp">
    MCP feature documentation
  </Card>

  <Card title="MCP Client" icon="code" href="/examples/mcp-client">
    WithMCPClients variant
  </Card>
</CardGroup>