---
title: Configuration
description: Config structs, YAML examples, and option helpers for MCP
---

## YAML Configuration Example

```yaml title="config.yaml"
extensions:
  mcp:
    enabled: true
    basePath: "/_/mcp"
    serverName: ""                   # defaults to app name
    serverVersion: ""                # defaults to app version

    # Auto-exposure
    autoExposeRoutes: true
    toolPrefix: ""
    excludePatterns: []
    includePatterns: []
    maxToolNameLength: 64

    # Capabilities
    enableResources: false
    enablePrompts: false

    # Security
    requireAuth: false
    authHeader: "Authorization"
    authTokens: []
    rateLimitPerMinute: 0            # 0 = unlimited

    # Performance
    enableMetrics: true
    schemaCache: true
```

The extension loads config from `extensions.mcp` first, falling back to `mcp`.

## Programmatic Configuration

```go
ext := mcp.NewExtension(
    mcp.WithBasePath("/_/mcp"),
    mcp.WithAutoExpose(true),
    mcp.WithToolPrefix("myapp_"),
    mcp.WithResources(true),
    mcp.WithPrompts(true),
)
```

## Config Struct Reference

### `Config`

| Field | Type | Default | Description |
|---|---|---|---|
| `Enabled` | `bool` | `true` | Enable the extension |
| `BasePath` | `string` | `"/_/mcp"` | Base path for MCP endpoints |
| `ServerName` | `string` | `""` | Server name (defaults to app name) |
| `ServerVersion` | `string` | `""` | Server version (defaults to app version) |
| `AutoExposeRoutes` | `bool` | `true` | Auto-expose HTTP routes as tools |
| `ToolPrefix` | `string` | `""` | Prefix for generated tool names |
| `ExcludePatterns` | `[]string` | `nil` | Route patterns to exclude |
| `IncludePatterns` | `[]string` | `nil` | Route patterns to include (whitelist) |
| `MaxToolNameLength` | `int` | `64` | Maximum tool name length |
| `EnableResources` | `bool` | `false` | Enable MCP resources |
| `EnablePrompts` | `bool` | `false` | Enable MCP prompts |
| `RequireAuth` | `bool` | `false` | Require authentication |
| `AuthHeader` | `string` | `"Authorization"` | Auth header name |
| `AuthTokens` | `[]string` | `nil` | Valid authentication tokens |
| `RateLimitPerMinute` | `int` | `0` | Rate limit (0 = unlimited) |
| `EnableMetrics` | `bool` | `true` | Enable metrics |
| `SchemaCache` | `bool` | `true` | Cache generated schemas |

## Option Helpers

| Function | Description |
|---|---|
| `WithEnabled(enabled)` | Toggle the extension |
| `WithBasePath(path)` | Set the base path for MCP endpoints |
| `WithAutoExpose(enabled)` | Toggle auto-exposure of routes |
| `WithToolPrefix(prefix)` | Set tool name prefix |
| `WithExcludePatterns(patterns...)` | Set route exclude patterns |
| `WithResources(enabled)` | Toggle MCP resources |
| `WithPrompts(enabled)` | Toggle MCP prompts |
| `WithAuth(header, tokens...)` | Enable authentication |
| `WithRateLimit(perMinute)` | Set rate limit |
| `WithConfig(config)` | Provide a complete config struct |