registry/docs/server-json/server.schema.json
Kalle Bylin 0ffcd36047
Add optional subfolder field to Repository schema (#363)
Adds 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.
2025-09-05 21:29:09 +01:00

467 lines
No EOL
15 KiB
JSON

{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"$id": "https://static.modelcontextprotocol.io/schemas/2025-07-09/server.schema.json",
"title": "MCP Server Detail",
"$ref": "#/$defs/ServerDetail",
"$defs": {
"Repository": {
"type": "object",
"required": [
"url",
"source"
],
"properties": {
"url": {
"type": "string",
"format": "uri",
"example": "https://github.com/modelcontextprotocol/servers"
},
"source": {
"type": "string",
"description": "Repository hosting service",
"example": "github"
},
"id": {
"type": "string",
"example": "b94b5f7e-c7c6-d760-2c78-a5e9b8a5b8c9"
},
"subfolder": {
"type": "string",
"description": "Optional relative path from repository root to the server location within a monorepo or nested package structure",
"example": "src/everything"
}
}
},
"VersionDetail": {
"type": "object",
"description": "Version information for this server. Defined as an object to allow for downstream extensibility (e.g. release_date)",
"required": [
"version"
],
"properties": {
"version": {
"type": "string",
"maxLength": 255,
"example": "1.0.2",
"description": "Version string for this server. SHOULD follow semantic versioning (e.g., '1.0.2', '2.1.0-alpha'). Equivalent of Implementation.version in MCP specification. Non-semantic versions are allowed but may not sort predictably."
}
}
},
"Server": {
"type": "object",
"required": [
"name",
"description",
"version_detail"
],
"properties": {
"name": {
"type": "string",
"description": "Server name/identifier",
"example": "io.modelcontextprotocol/filesystem",
"minLength": 1,
"maxLength": 200
},
"description": {
"type": "string",
"description": "Human-readable description of the server's functionality",
"example": "Node.js server implementing Model Context Protocol (MCP) for filesystem operations.",
"minLength": 1,
"maxLength": 100
},
"status": {
"type": "string",
"enum": ["active", "deprecated", "deleted"],
"default": "active",
"description": "Server lifecycle status. 'deprecated' indicates the server is no longer recommended for new usage. 'deleted' indicates the server should never be installed and existing installations should be uninstalled - this is rare, and usually indicates malware or a legal takedown."
},
"repository": {
"$ref": "#/$defs/Repository"
},
"version_detail": {
"$ref": "#/$defs/VersionDetail"
}
}
},
"Package": {
"type": "object",
"properties": {
"registry_type": {
"type": "string",
"description": "Registry type indicating how to download packages (e.g., 'npm', 'pypi', 'oci', 'nuget', 'mcpb')",
"examples": ["npm", "pypi", "oci", "nuget", "mcpb"]
},
"registry_base_url": {
"type": "string",
"format": "uri",
"description": "Base URL of the package registry",
"examples": ["https://registry.npmjs.org", "https://pypi.org", "https://docker.io", "https://api.nuget.org", "https://github.com", "https://gitlab.com"]
},
"identifier": {
"type": "string",
"description": "Package identifier - either a package name (for registries) or URL (for direct downloads)",
"examples": ["@modelcontextprotocol/server-brave-search", "https://github.com/example/releases/download/v1.0.0/package.mcpb"]
},
"version": {
"type": "string",
"description": "Package version",
"example": "1.0.2",
"minLength": 1
},
"file_sha256": {
"type": "string",
"description": "SHA-256 hash of the package file for integrity verification.",
"example": "fe333e598595000ae021bd27117db32ec69af6987f507ba7a63c90638ff633ce"
},
"runtime_hint": {
"type": "string",
"description": "A hint to help clients determine the appropriate runtime for the package. This field should be provided when `runtime_arguments` are present.",
"examples": [
"npx",
"uvx",
"docker",
"dnx"
]
},
"transport": {
"anyOf": [
{
"$ref": "#/$defs/StdioTransport"
},
{
"$ref": "#/$defs/StreamableHttpTransport"
},
{
"$ref": "#/$defs/SseTransport"
}
],
"description": "Transport protocol configuration for the package"
},
"runtime_arguments": {
"type": "array",
"description": "A list of arguments to be passed to the package's runtime command (such as docker or npx). The `runtime_hint` field should be provided when `runtime_arguments` are present.",
"items": {
"$ref": "#/$defs/Argument"
}
},
"package_arguments": {
"type": "array",
"description": "A list of arguments to be passed to the package's binary.",
"items": {
"$ref": "#/$defs/Argument"
}
},
"environment_variables": {
"type": "array",
"description": "A mapping of environment variables to be set when running the package.",
"items": {
"$ref": "#/$defs/KeyValueInput"
}
}
}
},
"Input": {
"type": "object",
"properties": {
"description": {
"description": "A description of the input, which clients can use to provide context to the user.",
"type": "string"
},
"is_required": {
"type": "boolean",
"default": false
},
"format": {
"type": "string",
"description": "Specifies the input format. Supported values include `filepath`, which should be interpreted as a file on the user's filesystem.\n\nWhen the input is converted to a string, booleans should be represented by the strings \"true\" and \"false\", and numbers should be represented as decimal values.",
"enum": [
"string",
"number",
"boolean",
"filepath"
],
"default": "string"
},
"value": {
"type": "string",
"description": "The default value for the input. If this is not set, the user may be prompted to provide a value. If a value is set, it should not be configurable by end users.\n\nIdentifiers wrapped in `{curly_braces}` will be replaced with the corresponding properties from the input `variables` map. If an identifier in braces is not found in `variables`, or if `variables` is not provided, the `{curly_braces}` substring should remain unchanged.\n"
},
"is_secret": {
"type": "boolean",
"description": "Indicates whether the input is a secret value (e.g., password, token). If true, clients should handle the value securely.",
"default": false
},
"default": {
"type": "string",
"description": "The default value for the input."
},
"choices": {
"type": "array",
"description": "A list of possible values for the input. If provided, the user must select one of these values.",
"items": {
"type": "string"
},
"example": []
}
}
},
"InputWithVariables": {
"allOf": [
{
"$ref": "#/$defs/Input"
},
{
"type": "object",
"properties": {
"variables": {
"type": "object",
"description": "A map of variable names to their values. Keys in the input `value` that are wrapped in `{curly_braces}` will be replaced with the corresponding variable values.",
"additionalProperties": {
"$ref": "#/$defs/Input"
}
}
}
}
]
},
"PositionalArgument": {
"description": "A positional input is a value inserted verbatim into the command line.",
"allOf": [
{
"$ref": "#/$defs/InputWithVariables"
},
{
"type": "object",
"required": [
"type"
],
"properties": {
"type": {
"type": "string",
"enum": [
"positional"
],
"example": "positional"
},
"value_hint": {
"type": "string",
"description": "An identifier-like hint for the value. This is not part of the command line, but can be used by client configuration and to provide hints to users.",
"example": "file_path"
},
"is_repeated": {
"type": "boolean",
"description": "Whether the argument can be repeated multiple times in the command line.",
"default": false
}
},
"anyOf": [
{
"required": [
"value_hint"
]
},
{
"required": [
"value"
]
}
]
}
]
},
"NamedArgument": {
"description": "A command-line `--flag={value}`.",
"allOf": [
{
"$ref": "#/$defs/InputWithVariables"
},
{
"type": "object",
"required": [
"type",
"name"
],
"properties": {
"type": {
"type": "string",
"enum": [
"named"
],
"example": "named"
},
"name": {
"type": "string",
"description": "The flag name, including any leading dashes.",
"example": "--port"
},
"is_repeated": {
"type": "boolean",
"description": "Whether the argument can be repeated multiple times.",
"default": false
}
}
}
]
},
"KeyValueInput": {
"allOf": [
{
"$ref": "#/$defs/InputWithVariables"
},
{
"type": "object",
"required": [
"name"
],
"properties": {
"name": {
"type": "string",
"description": "Name of the header or environment variable.",
"example": "SOME_VARIABLE"
}
}
}
]
},
"Argument": {
"anyOf": [
{
"$ref": "#/$defs/PositionalArgument"
},
{
"$ref": "#/$defs/NamedArgument"
}
]
},
"StdioTransport": {
"type": "object",
"required": [
"type"
],
"properties": {
"type": {
"type": "string",
"enum": [
"stdio"
],
"description": "Transport type",
"example": "stdio"
}
}
},
"StreamableHttpTransport": {
"type": "object",
"required": [
"type",
"url"
],
"properties": {
"type": {
"type": "string",
"enum": [
"streamable-http"
],
"description": "Transport type",
"example": "streamable-http"
},
"url": {
"type": "string",
"description": "URL template for the streamable-http transport. Variables in {curly_braces} reference argument value_hints, argument names, or environment variable names. After variable substitution, this should produce a valid URI.",
"example": "https://api.example.com/mcp"
},
"headers": {
"type": "array",
"description": "HTTP headers to include",
"items": {
"$ref": "#/$defs/KeyValueInput"
}
}
}
},
"SseTransport": {
"type": "object",
"required": [
"type",
"url"
],
"properties": {
"type": {
"type": "string",
"enum": [
"sse"
],
"description": "Transport type",
"example": "sse"
},
"url": {
"type": "string",
"format": "uri",
"description": "Server-Sent Events endpoint URL",
"example": "https://mcp-fs.example.com/sse"
},
"headers": {
"type": "array",
"description": "HTTP headers to include",
"items": {
"$ref": "#/$defs/KeyValueInput"
}
}
}
},
"ServerDetail": {
"description": "Schema for a static representation of an MCP server. Used in various contexts related to discovery, installation, and configuration.",
"allOf": [
{
"$ref": "#/$defs/Server"
},
{
"type": "object",
"properties": {
"$schema": {
"type": "string",
"format": "uri",
"description": "JSON Schema URI for this server.json format",
"example": "https://static.modelcontextprotocol.io/schemas/2025-07-09/server.schema.json"
},
"packages": {
"type": "array",
"items": {
"$ref": "#/$defs/Package"
}
},
"remotes": {
"type": "array",
"items": {
"anyOf": [
{
"$ref": "#/$defs/StreamableHttpTransport"
},
{
"$ref": "#/$defs/SseTransport"
}
]
}
},
"_meta": {
"type": "object",
"description": "Extension metadata using reverse DNS namespacing for vendor-specific data",
"additionalProperties": true,
"properties": {
"publisher": {
"type": "object",
"description": "Publisher-provided metadata for downstream registries",
"additionalProperties": true
},
"io.modelcontextprotocol.registry": {
"type": "object",
"description": "Official MCP registry metadata (read-only, added by registry)",
"additionalProperties": true
}
}
}
}
}
]
}
}
}