0ffcd36047Adds an optional `subfolder` field to the Repository object in server.json schema to support MCP servers located within subdirectories of monorepo structures. ## Motivation and Context Addresses issue #360 . The current MCP registry schema doesn't explicitly define how to reference servers that are located within a subdirectory of a Git repository (a "monorepo" structure). This is a common pattern (e.g., [microsoft/mcp](https://github.com/microsoft/mcp) & [awslabs/mcp](https://github.com/awslabs/mcp). ## How Has This Been Tested? - **Validator tests**: Added 6 new test cases covering valid subfolders and security validation (path traversal, absolute paths, invalid characters, etc.) - **Schema validation**: All 11 examples in `examples.md` validate successfully against both `server.schema.json` and `registry-schema.json` - **End-to-end validation**: Publisher tool (`mcp-publisher init`) works correctly and generates valid templates without subfolder - **Backward compatibility**: Existing server.json files without subfolder continue to work unchanged ## Breaking Changes **None.** This is a fully backward-compatible change: - The `subfolder` field is optional (uses `omitempty` JSON tag) - Existing server.json files work unchanged - Publisher tools generate valid templates without subfolder by default - All existing validation and schemas remain compatible ## Types of changes - [ ] Bug fix (non-breaking change which fixes an issue) - [x] New feature (non-breaking change which adds functionality) - [ ] Breaking change (fix or feature that would cause existing functionality to change) - [x] Documentation update ## Checklist - [x] I have read the [MCP Documentation](https://modelcontextprotocol.io) - [x] My code follows the repository's style guidelines - [x] New and existing tests pass locally - [x] I have added appropriate error handling - [x] I have added or updated documentation as needed ### Implementation Details **Schema Changes:** - Added `subfolder` property to Repository definition in `server.schema.json` and `openapi.yaml` - Field is optional with description and example (`"src/everything"`) **Go Model:** - Added `Subfolder string` field to Repository struct with `json:"subfolder,omitempty"` tag - Maintains backward compatibility through omitempty behavior **Security-Focused Validation:** - Validates subfolder is a clean relative path (no leading `/`) - Prevents path traversal attacks (no `..` sequences) - Blocks malformed paths (no trailing `/`, empty segments, invalid characters) - Uses regex validation for allowed characters: `^[a-zA-Z0-9\-_./]+$` **Documentation:** - Added monorepo example to `examples.md` demonstrating subfolder usage - Updated `repository_references.md` with concise subfolder documentation - Maintained consistency across all documentation with same example path **Testing:** - 6 new integration tests in validator covering security and format validation - Updated example count validation tool for new example - All existing tests continue to pass ### Design Decisions 1. **Optional by design**: Most servers don't need subfolder (single-repo pattern is common) 2. **Clean separation**: Repository URL stays clean, subfolder is separate metadata 3. **Security first**: Comprehensive validation prevents common path-based attacks 4. **Publisher tool unchanged**: Default templates don't include subfolder to avoid confusion for typical use cases This enables publishers with monorepo structures to clearly specify server locations while maintaining simplicity for the common single-repository case.
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Server JSON Examples
Basic Server with NPM Package
{
"$schema": "https://static.modelcontextprotocol.io/schemas/2025-07-09/server.schema.json",
"name": "io.modelcontextprotocol/brave-search",
"description": "MCP server for Brave Search API integration",
"status": "active",
"repository": {
"url": "https://github.com/modelcontextprotocol/servers",
"source": "github"
},
"version_detail": {
"version": "1.0.2"
},
"packages": [
{
"registry_type": "npm",
"registry_base_url": "https://registry.npmjs.org",
"identifier": "@modelcontextprotocol/server-brave-search",
"version": "1.0.2",
"transport": {
"type": "stdio"
},
"environment_variables": [
{
"name": "BRAVE_API_KEY",
"description": "Brave Search API Key",
"is_required": true,
"is_secret": true
}
]
}
],
"_meta": {
"publisher": {
"tool": "npm-publisher",
"version": "1.0.1",
"build_info": {
"timestamp": "2023-12-01T10:30:00Z"
}
}
}
}
Server in a Monorepo with Subfolder
For MCP servers located within a subdirectory of a larger repository (monorepo structure), use the subfolder field to specify the relative path:
{
"$schema": "https://static.modelcontextprotocol.io/schemas/2025-07-09/server.schema.json",
"name": "io.modelcontextprotocol/everything",
"description": "MCP server that exercises all the features of the MCP protocol",
"status": "active",
"repository": {
"url": "https://github.com/modelcontextprotocol/servers",
"source": "github",
"subfolder": "src/everything"
},
"version_detail": {
"version": "0.6.2"
},
"packages": [
{
"registry_type": "npm",
"registry_base_url": "https://registry.npmjs.org",
"identifier": "@modelcontextprotocol/everything",
"version": "0.6.2",
"transport": {
"type": "stdio"
}
}
],
"_meta": {
"publisher": {
"tool": "npm-publisher",
"version": "1.0.1",
"build_info": {
"timestamp": "2023-12-01T10:30:00Z"
}
}
}
}
Constant (fixed) arguments needed to start the MCP server
Suppose your MCP server application requires a mcp start CLI arguments to start in MCP server mode. Express these as positional arguments like this:
{
"name": "io.github.joelverhagen/knapcode-samplemcpserver",
"description": "Sample NuGet MCP server for a random number and random weather",
"version_detail": {
"version": "0.4.0-beta"
},
"packages": [
{
"registry_type": "nuget",
"registry_base_url": "https://api.nuget.org",
"identifier": "Knapcode.SampleMcpServer",
"version": "0.4.0-beta",
"transport": {
"type": "stdio"
},
"package_arguments": [
{
"type": "positional",
"value": "mcp"
},
{
"type": "positional",
"value": "start"
}
]
}
],
"_meta": {
"publisher": {
"tool": "nuget-publisher",
"version": "2.1.0",
"build_info": {
"timestamp": "2023-11-15T14:22:00Z",
"pipeline_id": "nuget-build-456"
}
}
}
}
This will essentially instruct the MCP client to execute dnx Knapcode.SampleMcpServer@0.4.0-beta -- mcp start instead of the default dnx Knapcode.SampleMcpServer@0.4.0-beta (when no package_arguments are provided).
Filesystem Server with Multiple Packages
{
"$schema": "https://static.modelcontextprotocol.io/schemas/2025-07-09/server.schema.json",
"name": "io.github.modelcontextprotocol/filesystem",
"description": "Node.js server implementing Model Context Protocol (MCP) for filesystem operations.",
"status": "active",
"repository": {
"url": "https://github.com/modelcontextprotocol/servers",
"source": "github",
"id": "b94b5f7e-c7c6-d760-2c78-a5e9b8a5b8c9"
},
"version_detail": {
"version": "1.0.2"
},
"packages": [
{
"registry_type": "npm",
"registry_base_url": "https://registry.npmjs.org",
"identifier": "@modelcontextprotocol/server-filesystem",
"version": "1.0.2",
"transport": {
"type": "stdio"
},
"package_arguments": [
{
"type": "positional",
"value_hint": "target_dir",
"description": "Path to access",
"default": "/Users/username/Desktop",
"is_required": true,
"is_repeated": true
}
],
"environment_variables": [
{
"name": "LOG_LEVEL",
"description": "Logging level (debug, info, warn, error)",
"default": "info"
}
]
},
{
"registry_type": "oci",
"registry_base_url": "https://docker.io",
"identifier": "mcp/filesystem",
"version": "1.0.2",
"transport": {
"type": "stdio"
},
"runtime_arguments": [
{
"type": "named",
"description": "Mount a volume into the container",
"name": "--mount",
"value": "type=bind,src={source_path},dst={target_path}",
"is_required": true,
"is_repeated": true,
"variables": {
"source_path": {
"description": "Source path on host",
"format": "filepath",
"is_required": true
},
"target_path": {
"description": "Path to mount in the container. It should be rooted in `/project` directory.",
"is_required": true,
"default": "/project"
}
}
}
],
"package_arguments": [
{
"type": "positional",
"value_hint": "target_dir",
"value": "/project"
}
],
"environment_variables": [
{
"name": "LOG_LEVEL",
"description": "Logging level (debug, info, warn, error)",
"default": "info"
}
]
}
],
"_meta": {
"publisher": {
"tool": "ci-publisher",
"version": "3.2.1",
"build_info": {
"commit": "a1b2c3d4e5f6789",
"timestamp": "2023-12-01T10:30:00Z",
"pipeline_id": "filesystem-build-789",
"environment": "production"
}
}
}
}
Remote Server Example
{
"name": "io.modelcontextprotocol.anonymous/mcp-fs",
"description": "Cloud-hosted MCP filesystem server",
"repository": {
"url": "https://github.com/example/remote-fs",
"source": "github",
"id": "xyz789ab-cdef-0123-4567-890ghijklmno"
},
"version_detail": {
"version": "2.0.0"
},
"remotes": [
{
"type": "sse",
"url": "http://mcp-fs.anonymous.modelcontextprotocol.io/sse"
}
],
"_meta": {
"publisher": {
"tool": "cloud-deployer",
"version": "2.4.0",
"build_info": {
"commit": "f7e8d9c2b1a0",
"timestamp": "2023-12-05T08:45:00Z",
"deployment_id": "remote-fs-deploy-456",
"region": "us-west-2"
}
}
}
}
Python Package Example
{
"name": "io.github.example/weather-mcp",
"description": "Python MCP server for weather data access",
"repository": {
"url": "https://github.com/example/weather-mcp",
"source": "github",
"id": "def456gh-ijkl-7890-mnop-qrstuvwxyz12"
},
"version_detail": {
"version": "0.5.0"
},
"packages": [
{
"registry_type": "pypi",
"registry_base_url": "https://pypi.org",
"identifier": "weather-mcp-server",
"version": "0.5.0",
"runtime_hint": "uvx",
"transport": {
"type": "stdio"
},
"environment_variables": [
{
"name": "WEATHER_API_KEY",
"description": "API key for weather service",
"is_required": true,
"is_secret": true
},
{
"name": "WEATHER_UNITS",
"description": "Temperature units (celsius, fahrenheit)",
"default": "celsius"
}
]
}
],
"_meta": {
"publisher": {
"tool": "poetry-publisher",
"version": "1.8.3",
"build_info": {
"python_version": "3.11.5",
"timestamp": "2023-11-28T16:20:00Z",
"build_id": "pypi-weather-123",
"dependencies_hash": "sha256:a9b8c7d6e5f4"
}
}
}
}
NuGet (.NET) Package Example
The dnx tool ships with the .NET 10 SDK, starting with Preview 6.
{
"name": "io.github.joelverhagen/knapcode-samplemcpserver",
"description": "Sample NuGet MCP server for a random number and random weather",
"repository": {
"url": "https://github.com/joelverhagen/Knapcode.SampleMcpServer",
"source": "github",
"id": "example-nuget-id-0000-1111-222222222222"
},
"version_detail": {
"version": "0.5.0"
},
"packages": [
{
"registry_type": "nuget",
"registry_base_url": "https://api.nuget.org",
"identifier": "Knapcode.SampleMcpServer",
"version": "0.5.0",
"runtime_hint": "dnx",
"transport": {
"type": "stdio"
},
"environment_variables": [
{
"name": "WEATHER_CHOICES",
"description": "Comma separated list of weather descriptions to randomly select.",
"is_required": true,
"is_secret": false
}
]
}
],
"_meta": {
"publisher": {
"tool": "dotnet-publisher",
"version": "8.0.100",
"build_info": {
"dotnet_version": "8.0.0",
"timestamp": "2023-12-10T12:15:00Z",
"configuration": "Release",
"target_framework": "net8.0",
"build_number": "20231210.1"
}
}
}
}
Complex Docker Server with Multiple Arguments
{
"name": "io.github.example/database-manager",
"description": "MCP server for database operations with support for multiple database types",
"repository": {
"url": "https://github.com/example/database-manager-mcp",
"source": "github",
"id": "ghi789jk-lmno-1234-pqrs-tuvwxyz56789"
},
"version_detail": {
"version": "3.1.0"
},
"packages": [
{
"registry_type": "oci",
"registry_base_url": "https://docker.io",
"identifier": "example/database-manager-mcp",
"version": "3.1.0",
"transport": {
"type": "stdio"
},
"runtime_arguments": [
{
"type": "named",
"name": "--network",
"value": "host",
"description": "Use host network mode"
},
{
"type": "named",
"name": "-e",
"value": "DB_TYPE={db_type}",
"description": "Database type to connect to",
"is_repeated": true,
"variables": {
"db_type": {
"description": "Type of database",
"choices": [
"postgres",
"mysql",
"mongodb",
"redis"
],
"is_required": true
}
}
}
],
"package_arguments": [
{
"type": "named",
"name": "--host",
"description": "Database host",
"default": "localhost",
"is_required": true
},
{
"type": "named",
"name": "--port",
"description": "Database port",
"format": "number"
},
{
"type": "positional",
"value_hint": "database_name",
"description": "Name of the database to connect to",
"is_required": true
}
],
"environment_variables": [
{
"name": "DB_USERNAME",
"description": "Database username",
"is_required": true
},
{
"name": "DB_PASSWORD",
"description": "Database password",
"is_required": true,
"is_secret": true
},
{
"name": "SSL_MODE",
"description": "SSL connection mode",
"default": "prefer",
"choices": [
"disable",
"prefer",
"require"
]
}
]
}
],
"_meta": {
"publisher": {
"tool": "docker-buildx",
"version": "0.12.1",
"build_info": {
"docker_version": "24.0.7",
"timestamp": "2023-12-08T14:30:00Z",
"platform": "linux/amd64,linux/arm64",
"registry": "docker.io",
"image_digest": "sha256:1a2b3c4d5e6f7890"
}
}
}
}
Server with Remote and Package Options
{
"$schema": "https://static.modelcontextprotocol.io/schemas/2025-07-09/server.schema.json",
"name": "io.modelcontextprotocol.anonymous/hybrid-mcp",
"description": "MCP server available as both local package and remote service",
"repository": {
"url": "https://github.com/example/hybrid-mcp",
"source": "github",
"id": "klm012no-pqrs-3456-tuvw-xyz789abcdef"
},
"version_detail": {
"version": "1.5.0"
},
"packages": [
{
"registry_type": "npm",
"registry_base_url": "https://registry.npmjs.org",
"identifier": "@example/hybrid-mcp-server",
"version": "1.5.0",
"runtime_hint": "npx",
"transport": {
"type": "stdio"
},
"package_arguments": [
{
"type": "named",
"name": "--mode",
"description": "Operation mode",
"default": "local",
"choices": [
"local",
"cached",
"proxy"
]
}
]
}
],
"remotes": [
{
"type": "sse",
"url": "https://mcp.anonymous.modelcontextprotocol.io/sse",
"headers": [
{
"name": "X-API-Key",
"description": "API key for authentication",
"is_required": true,
"is_secret": true
},
{
"name": "X-Region",
"description": "Service region",
"default": "us-east-1",
"choices": [
"us-east-1",
"eu-west-1",
"ap-southeast-1"
]
}
]
},
{
"type": "streamable-http",
"url": "https://mcp.anonymous.modelcontextprotocol.io/http"
}
],
"_meta": {
"publisher": {
"tool": "hybrid-deployer",
"version": "1.7.2",
"build_info": {
"timestamp": "2023-12-03T11:00:00Z",
"deployment_strategy": "blue-green",
"npm_version": "10.2.4",
"node_version": "20.10.0",
"service_endpoints": {
"sse": "deployed",
"streamable": "deployed"
}
}
}
}
}
MCP Bundle (MCPB) Package Example
{
"name": "io.modelcontextprotocol/text-editor",
"description": "MCP Bundle server for advanced text editing capabilities",
"repository": {
"url": "https://github.com/modelcontextprotocol/text-editor-mcpb",
"source": "github"
},
"version_detail": {
"version": "1.0.2"
},
"packages": [
{
"registry_type": "mcpb",
"registry_base_url": "https://github.com",
"identifier": "https://github.com/modelcontextprotocol/text-editor-mcpb/releases/download/v1.0.2/text-editor.mcpb",
"version": "1.0.2",
"file_sha256": "fe333e598595000ae021bd27117db32ec69af6987f507ba7a63c90638ff633ce",
"transport": {
"type": "stdio"
}
}
],
"_meta": {
"publisher": {
"tool": "mcpb-publisher",
"version": "1.0.0",
"build_info": {
"timestamp": "2023-12-02T09:15:00Z",
"bundle_format": "mcpb-v1"
}
}
}
}
This example shows an MCPB (MCP Bundle) package that:
- Is hosted on GitHub Releases (an allowlisted provider)
- Includes a SHA-256 hash for integrity verification
- Can be downloaded and executed directly by MCP clients that support MCPB
Deprecated Server Example
{
"name": "io.github.example/old-weather",
"description": "Legacy weather server - DEPRECATED: Use weather-v2 instead for new projects",
"status": "deprecated",
"repository": {
"url": "https://github.com/example/old-weather",
"source": "github",
"id": "legacy-abc123-def456-789012-345678-901234567890"
},
"version_detail": {
"version": "0.9.5"
},
"packages": [
{
"registry_type": "npm",
"registry_base_url": "https://registry.npmjs.org",
"identifier": "@legacy/old-weather-server",
"version": "0.9.5",
"transport": {
"type": "stdio"
},
"environment_variables": [
{
"name": "WEATHER_API_KEY",
"description": "Weather API key",
"is_required": true,
"is_secret": true
}
]
}
],
"_meta": {
"publisher": {
"tool": "legacy-publisher",
"version": "0.8.1",
"build_info": {
"timestamp": "2023-06-15T09:30:00Z",
"deprecation_notice": "This publisher is deprecated. Use npm-publisher v2.0+ for new projects.",
"maintenance_mode": true,
"final_version": true
}
}
}
}