diff --git a/docs/reference/api/openapi.yaml b/docs/reference/api/openapi.yaml index 59d941ae..3dc84b5a 100644 --- a/docs/reference/api/openapi.yaml +++ b/docs/reference/api/openapi.yaml @@ -440,10 +440,7 @@ components: description: A hint to help clients determine the appropriate runtime for the package. This field should be provided when `runtimeArguments` are present. examples: [npx, uvx, docker, dnx] transport: - anyOf: - - $ref: '#/components/schemas/StdioTransport' - - $ref: '#/components/schemas/StreamableHttpTransport' - - $ref: '#/components/schemas/SseTransport' + $ref: '#/components/schemas/LocalTransport' description: Transport protocol configuration for the package runtimeArguments: type: array @@ -599,8 +596,9 @@ components: example: "streamable-http" url: type: string - description: URL template for the streamable-http transport. Variables in {curly_braces} reference argument valueHints, argument names, or environment variable names. After variable substitution, this should produce a valid URI. + description: "URL template for the streamable-http transport. Variables in {curly_braces} are resolved based on context: In Package context, they reference argument valueHints, argument names, or environment variable names from the parent Package. In Remote context, they reference variables from the transport's 'variables' object. After variable substitution, this should produce a valid URI." example: "https://api.example.com/mcp" + pattern: "^https?://[^\\s]+$" headers: type: array description: HTTP headers to include @@ -620,15 +618,36 @@ components: example: "sse" url: type: string - format: uri - description: Server-Sent Events endpoint URL + description: "Server-Sent Events endpoint URL template. Variables in {curly_braces} are resolved based on context: In Package context, they reference argument valueHints, argument names, or environment variable names from the parent Package. In Remote context, they reference variables from the transport's 'variables' object. After variable substitution, this should produce a valid URI." example: "https://mcp-fs.example.com/sse" + pattern: "^https?://[^\\s]+$" headers: type: array description: HTTP headers to include items: $ref: '#/components/schemas/KeyValueInput' + LocalTransport: + anyOf: + - $ref: '#/components/schemas/StdioTransport' + - $ref: '#/components/schemas/StreamableHttpTransport' + - $ref: '#/components/schemas/SseTransport' + description: Transport protocol configuration for local/package context + + RemoteTransport: + allOf: + - anyOf: + - $ref: '#/components/schemas/StreamableHttpTransport' + - $ref: '#/components/schemas/SseTransport' + - type: object + properties: + variables: + type: object + description: "Configuration variables that can be referenced in URL template {curly_braces}. The key is the variable name, and the value defines the variable properties." + additionalProperties: + $ref: '#/components/schemas/Input' + description: Transport protocol configuration for remote context - extends StreamableHttpTransport or SseTransport with variables + Icon: type: object description: An optionally-sized icon that can be displayed in a user interface. @@ -717,9 +736,7 @@ components: remotes: type: array items: - anyOf: - - $ref: '#/components/schemas/StreamableHttpTransport' - - $ref: '#/components/schemas/SseTransport' + $ref: '#/components/schemas/RemoteTransport' _meta: type: object description: "Extension metadata using reverse DNS namespacing for vendor-specific data" diff --git a/docs/reference/server-json/generic-server-json.md b/docs/reference/server-json/generic-server-json.md index 302a4449..875f570b 100644 --- a/docs/reference/server-json/generic-server-json.md +++ b/docs/reference/server-json/generic-server-json.md @@ -688,3 +688,90 @@ For MCP servers that follow a custom installation path or are embedded in applic } ``` + +### Remote Server with URL Templating + +This example demonstrates URL templating for remote servers, useful for multi-tenant deployments where each instance has its own endpoint. Unlike Package transports (which reference parent arguments/environment variables), Remote transports define their own variables: + +```json +{ + "$schema": "https://static.modelcontextprotocol.io/schemas/2025-10-17/server.schema.json", + "name": "io.modelcontextprotocol.anonymous/multi-tenant-server", + "description": "MCP server with configurable remote endpoint", + "title": "Multi-Tenant Server", + "version": "1.0.0", + "remotes": [ + { + "type": "streamable-http", + "url": "https://anonymous.modelcontextprotocol.io/mcp/{tenant_id}", + "variables": { + "tenant_id": { + "description": "Tenant identifier (e.g., 'us-cell1', 'emea-cell1')", + "isRequired": true + } + } + } + ] +} +``` + +Clients configure the tenant identifier, and the `{tenant_id}` variable in the URL gets replaced with the provided variable value to connect to the appropriate tenant endpoint (e.g., `https://anonymous.modelcontextprotocol.io/mcp/us-cell1` or `https://anonymous.modelcontextprotocol.io/mcp/emea-cell1`). + +The same URL templating works with SSE transport: + +```json +{ + "$schema": "https://static.modelcontextprotocol.io/schemas/2025-10-17/server.schema.json", + "name": "io.modelcontextprotocol.anonymous/events-server", + "description": "MCP server using SSE with tenant-specific endpoints", + "version": "1.0.0", + "remotes": [ + { + "type": "sse", + "url": "https://events.anonymous.modelcontextprotocol.io/sse/{tenant_id}", + "variables": { + "tenant_id": { + "description": "Tenant identifier", + "isRequired": true + } + } + } + ] +} +``` + +### Local Server with URL Templating + +This example demonstrates URL templating for local/package servers, where variables reference parent Package arguments or environment variables: + +```json +{ + "$schema": "https://static.modelcontextprotocol.io/schemas/2025-10-17/server.schema.json", + "name": "io.github.example/configurable-server", + "description": "Local MCP server with configurable port", + "title": "Configurable Server", + "version": "1.0.0", + "packages": [ + { + "registryType": "npm", + "registryBaseUrl": "https://registry.npmjs.org", + "identifier": "@example/mcp-server", + "version": "1.0.0", + "transport": { + "type": "streamable-http", + "url": "http://localhost:{--port}/mcp" + }, + "packageArguments": [ + { + "type": "named", + "name": "--port", + "description": "Port for the server to listen on", + "default": "3000" + } + ] + } + ] +} +``` + +The `{--port}` variable in the URL references the `--port` argument `name` from packageArguments. For positional arguments, an argument with the `valueHint` of `port` could similarly be referenced as `{port}`. When the package runs with `--port 8080`, the URL becomes `http://localhost:8080/mcp`. diff --git a/docs/reference/server-json/server.schema.json b/docs/reference/server-json/server.schema.json index 2d55b589..703ca0aa 100644 --- a/docs/reference/server-json/server.schema.json +++ b/docs/reference/server-json/server.schema.json @@ -156,6 +156,20 @@ } ] }, + "LocalTransport": { + "anyOf": [ + { + "$ref": "#/definitions/StdioTransport" + }, + { + "$ref": "#/definitions/StreamableHttpTransport" + }, + { + "$ref": "#/definitions/SseTransport" + } + ], + "description": "Transport protocol configuration for local/package context" + }, "NamedArgument": { "allOf": [ { @@ -262,17 +276,7 @@ "type": "string" }, "transport": { - "anyOf": [ - { - "$ref": "#/definitions/StdioTransport" - }, - { - "$ref": "#/definitions/StreamableHttpTransport" - }, - { - "$ref": "#/definitions/SseTransport" - } - ], + "$ref": "#/definitions/LocalTransport", "description": "Transport protocol configuration for the package" }, "version": { @@ -337,6 +341,33 @@ ], "description": "A positional input is a value inserted verbatim into the command line." }, + "RemoteTransport": { + "allOf": [ + { + "anyOf": [ + { + "$ref": "#/definitions/StreamableHttpTransport" + }, + { + "$ref": "#/definitions/SseTransport" + } + ] + }, + { + "properties": { + "variables": { + "additionalProperties": { + "$ref": "#/definitions/Input" + }, + "description": "Configuration variables that can be referenced in URL template {curly_braces}. The key is the variable name, and the value defines the variable properties.", + "type": "object" + } + }, + "type": "object" + } + ], + "description": "Transport protocol configuration for remote context - extends StreamableHttpTransport or SseTransport with variables" + }, "Repository": { "description": "Repository metadata for the MCP server source code. Enables users and security experts to inspect the code, improving transparency.", "properties": { @@ -427,14 +458,7 @@ }, "remotes": { "items": { - "anyOf": [ - { - "$ref": "#/definitions/StreamableHttpTransport" - }, - { - "$ref": "#/definitions/SseTransport" - } - ] + "$ref": "#/definitions/RemoteTransport" }, "type": "array" }, @@ -487,9 +511,9 @@ "type": "string" }, "url": { - "description": "Server-Sent Events endpoint URL", + "description": "Server-Sent Events endpoint URL template. Variables in {curly_braces} are resolved based on context: In Package context, they reference argument valueHints, argument names, or environment variable names from the parent Package. In Remote context, they reference variables from the transport's 'variables' object. After variable substitution, this should produce a valid URI.", "example": "https://mcp-fs.example.com/sse", - "format": "uri", + "pattern": "^https?://[^\\s]+$", "type": "string" } }, @@ -533,8 +557,9 @@ "type": "string" }, "url": { - "description": "URL template for the streamable-http transport. Variables in {curly_braces} reference argument valueHints, argument names, or environment variable names. After variable substitution, this should produce a valid URI.", + "description": "URL template for the streamable-http transport. Variables in {curly_braces} are resolved based on context: In Package context, they reference argument valueHints, argument names, or environment variable names from the parent Package. In Remote context, they reference variables from the transport's 'variables' object. After variable substitution, this should produce a valid URI.", "example": "https://api.example.com/mcp", + "pattern": "^https?://[^\\s]+$", "type": "string" } }, diff --git a/internal/validators/constants.go b/internal/validators/constants.go index dce640fe..90dec391 100644 --- a/internal/validators/constants.go +++ b/internal/validators/constants.go @@ -13,8 +13,9 @@ var ( ErrReservedVersionString = errors.New("version string 'latest' is reserved and cannot be used") ErrVersionLooksLikeRange = errors.New("version must be a specific version, not a range") - // Remote validation errors - ErrInvalidRemoteURL = errors.New("invalid remote URL") + // Transport validation errors + ErrInvalidPackageTransportURL = errors.New("invalid package transport URL") + ErrInvalidRemoteURL = errors.New("invalid remote URL") // Registry validation errors ErrUnsupportedRegistryBaseURL = errors.New("unsupported registry base URL") diff --git a/internal/validators/utils.go b/internal/validators/utils.go index 9a6b4cf5..035132db 100644 --- a/internal/validators/utils.go +++ b/internal/validators/utils.go @@ -61,7 +61,13 @@ func replaceTemplateVariables(rawURL string) string { result = strings.ReplaceAll(result, placeholder, replacement) } - // Handle any remaining {variable} patterns with generic placeholder + // Handle any remaining {variable} patterns with context-appropriate placeholders + // If the variable is in a port position (after a colon in the host), use a numeric placeholder + // Pattern: :/{variable} or :{variable}/ or :{variable} at end + portRe := regexp.MustCompile(`:(\{[^}]+\})(/|$)`) + result = portRe.ReplaceAllString(result, ":8080$2") + + // Replace any other remaining {variable} patterns with generic placeholder re := regexp.MustCompile(`\{[^}]+\}`) result = re.ReplaceAllString(result, "placeholder") @@ -132,8 +138,11 @@ func IsValidRemoteURL(rawURL string) bool { return false } + // Replace template variables with placeholders before parsing for localhost check + testURL := replaceTemplateVariables(rawURL) + // Parse the URL to check for localhost restriction - u, err := url.Parse(rawURL) + u, err := url.Parse(testURL) if err != nil { return false } @@ -153,8 +162,8 @@ func IsValidRemoteURL(rawURL string) bool { // IsValidTemplatedURL validates a URL with template variables against available variables // For packages: validates that template variables reference package arguments or environment variables -// For remotes: disallows template variables entirely -func IsValidTemplatedURL(rawURL string, availableVariables []string, allowTemplates bool) bool { +// For remotes: validates that template variables reference the transport's variables map +func IsValidTemplatedURL(rawURL string, availableVariables []string) bool { // First check basic URL structure if !IsValidURL(rawURL) { return false @@ -168,11 +177,6 @@ func IsValidTemplatedURL(rawURL string, availableVariables []string, allowTempla return true } - // If templates are not allowed (e.g., for remotes), reject URLs with templates - if !allowTemplates { - return false - } - // Validate that all template variables are available availableSet := make(map[string]bool) for _, v := range availableVariables { diff --git a/internal/validators/validators.go b/internal/validators/validators.go index 3c9789df..1085474a 100644 --- a/internal/validators/validators.go +++ b/internal/validators/validators.go @@ -363,6 +363,20 @@ func collectAvailableVariables(pkg *model.Package) []string { return variables } +// collectRemoteTransportVariables extracts available variable names from a remote transport +func collectRemoteTransportVariables(transport *model.Transport) []string { + var variables []string + + // Add variable names from the Variables map + for variableName := range transport.Variables { + if variableName != "" { + variables = append(variables, variableName) + } + } + + return variables +} + // validatePackageTransport validates a package's transport with templating support func validatePackageTransport(transport *model.Transport, availableVariables []string) error { // Validate transport type is supported @@ -379,14 +393,14 @@ func validatePackageTransport(transport *model.Transport, availableVariables []s return fmt.Errorf("url is required for %s transport type", transport.Type) } // Validate URL format with template variable support - if !IsValidTemplatedURL(transport.URL, availableVariables, true) { + if !IsValidTemplatedURL(transport.URL, availableVariables) { // Check if it's a template variable issue or basic URL issue templateVars := extractTemplateVariables(transport.URL) if len(templateVars) > 0 { return fmt.Errorf("%w: template variables in URL %s reference undefined variables. Available variables: %v", - ErrInvalidRemoteURL, transport.URL, availableVariables) + ErrInvalidPackageTransportURL, transport.URL, availableVariables) } - return fmt.Errorf("%w: %s", ErrInvalidRemoteURL, transport.URL) + return fmt.Errorf("%w: %s", ErrInvalidPackageTransportURL, transport.URL) } return nil default: @@ -394,7 +408,7 @@ func validatePackageTransport(transport *model.Transport, availableVariables []s } } -// validateRemoteTransport validates a remote transport (no templating allowed) +// validateRemoteTransport validates a remote transport with optional templating func validateRemoteTransport(obj *model.Transport) error { // Validate transport type is supported - remotes only support streamable-http and sse switch obj.Type { @@ -403,7 +417,22 @@ func validateRemoteTransport(obj *model.Transport) error { if obj.URL == "" { return fmt.Errorf("url is required for %s transport type", obj.Type) } - // Validate URL format (no templates allowed for remotes, no localhost) + + // Collect available variables from the transport's Variables field + availableVariables := collectRemoteTransportVariables(obj) + + // Validate URL format with template variable support + if !IsValidTemplatedURL(obj.URL, availableVariables) { + // Check if it's a template variable issue or basic URL issue + templateVars := extractTemplateVariables(obj.URL) + if len(templateVars) > 0 { + return fmt.Errorf("%w: template variables in URL %s reference undefined variables. Available variables: %v", + ErrInvalidRemoteURL, obj.URL, availableVariables) + } + return fmt.Errorf("%w: %s", ErrInvalidRemoteURL, obj.URL) + } + + // Additional check: reject localhost URLs for remotes (like the old IsValidRemoteURL did) if !IsValidRemoteURL(obj.URL) { return fmt.Errorf("%w: %s", ErrInvalidRemoteURL, obj.URL) } diff --git a/internal/validators/validators_test.go b/internal/validators/validators_test.go index e5d39092..7b695879 100644 --- a/internal/validators/validators_test.go +++ b/internal/validators/validators_test.go @@ -1598,6 +1598,138 @@ func TestValidate_TransportValidation(t *testing.T) { }, expectedError: "invalid remote URL", }, + // Remote transport variable tests + { + name: "remote transport with URL variables - valid", + serverDetail: apiv0.ServerJSON{ + Schema: model.CurrentSchemaURL, + Name: "com.example/test-server", + Description: "A test server", + Version: "1.0.0", + Remotes: []model.Transport{ + { + Type: "streamable-http", + URL: "https://example.com/mcp/{tenant_id}", + Variables: map[string]model.Input{ + "tenant_id": { + Description: "Tenant identifier", + IsRequired: true, + }, + }, + }, + }, + }, + expectedError: "", + }, + { + name: "remote transport with multiple URL variables - valid", + serverDetail: apiv0.ServerJSON{ + Schema: model.CurrentSchemaURL, + Name: "com.example/test-server", + Description: "A test server", + Version: "1.0.0", + Remotes: []model.Transport{ + { + Type: "streamable-http", + URL: "https://{region}.example.com/mcp/{tenant_id}", + Variables: map[string]model.Input{ + "region": { + Description: "Server region", + Choices: []string{"us-east-1", "eu-west-1"}, + }, + "tenant_id": { + Description: "Tenant identifier", + IsRequired: true, + }, + }, + }, + }, + }, + expectedError: "", + }, + { + name: "remote transport with undefined URL variable - invalid", + serverDetail: apiv0.ServerJSON{ + Schema: model.CurrentSchemaURL, + Name: "com.example/test-server", + Description: "A test server", + Version: "1.0.0", + Remotes: []model.Transport{ + { + Type: "streamable-http", + URL: "https://example.com/mcp/{tenant_id}", + // Missing variables definition + }, + }, + }, + expectedError: "template variables in URL", + }, + { + name: "remote transport with missing variable in URL - invalid", + serverDetail: apiv0.ServerJSON{ + Schema: model.CurrentSchemaURL, + Name: "com.example/test-server", + Description: "A test server", + Version: "1.0.0", + Remotes: []model.Transport{ + { + Type: "streamable-http", + URL: "https://example.com/mcp/{tenant_id}/{region}", + Variables: map[string]model.Input{ + "tenant_id": { + Description: "Tenant identifier", + }, + // Missing "region" variable + }, + }, + }, + }, + expectedError: "template variables in URL", + }, + { + name: "remote transport SSE with URL variables - valid", + serverDetail: apiv0.ServerJSON{ + Schema: model.CurrentSchemaURL, + Name: "com.example/test-server", + Description: "A test server", + Version: "1.0.0", + Remotes: []model.Transport{ + { + Type: "sse", + URL: "https://events.example.com/mcp/{api_key}", + Variables: map[string]model.Input{ + "api_key": { + Description: "API key for authentication", + IsRequired: true, + IsSecret: true, + }, + }, + }, + }, + }, + expectedError: "", + }, + { + name: "remote transport with variables but no template in URL - valid", + serverDetail: apiv0.ServerJSON{ + Schema: model.CurrentSchemaURL, + Name: "com.example/test-server", + Description: "A test server", + Version: "1.0.0", + Remotes: []model.Transport{ + { + Type: "streamable-http", + URL: "https://example.com/mcp", + Variables: map[string]model.Input{ + "unused_var": { + Description: "This variable is defined but not used", + }, + }, + }, + }, + }, + expectedError: "", // Valid - variables can be defined but not used + }, } for _, tt := range tests { diff --git a/pkg/model/types.go b/pkg/model/types.go index 454e2255..8a7443d8 100644 --- a/pkg/model/types.go +++ b/pkg/model/types.go @@ -8,10 +8,13 @@ const ( StatusDeleted Status = "deleted" ) +// Transport represents transport configuration for both Package and Remote contexts. +// For Remote context, the Variables field can be used for URL templating. type Transport struct { - Type string `json:"type" doc:"Transport type (stdio, streamable-http, or sse)" example:"stdio"` - URL string `json:"url,omitempty" doc:"URL for streamable-http or sse transports" example:"https://api.example.com/mcp"` - Headers []KeyValueInput `json:"headers,omitempty" doc:"HTTP headers for streamable-http or sse transports"` + Type string `json:"type" doc:"Transport type (stdio, streamable-http, or sse)" example:"stdio"` + URL string `json:"url,omitempty" doc:"URL for streamable-http or sse transports" example:"https://api.example.com/mcp"` + Headers []KeyValueInput `json:"headers,omitempty" doc:"HTTP headers for streamable-http or sse transports"` + Variables map[string]Input `json:"variables,omitempty" doc:"Variables for URL templating in remote transports"` } // Package represents a package configuration. diff --git a/tools/validate-examples/main.go b/tools/validate-examples/main.go index 41d8ba05..2e021a68 100644 --- a/tools/validate-examples/main.go +++ b/tools/validate-examples/main.go @@ -33,7 +33,7 @@ func main() { func runValidation() error { // Define what we validate and how - expectedServerJSONCount := 12 + expectedServerJSONCount := 15 targets := []validationTarget{ { path: filepath.Join("docs", "reference", "server-json", "generic-server-json.md"),