fc88cf0870Added schema validation and support for exhaustive and more detailed validation to existing validators. Added new `mcp-publisher validate` command. No change to any existing tests or behavior other than the new command. ## Motivation and Context Many currently published servers fail schema validation. Of those that pass, many have semantic/logical errors or other errors that make them impossible to configure, or their configuration when applied doesn't generate correct MCP server configuration (per their own documentation). To address this, we need better tooling to validate servers and to inform server publishers of errors, issues, and best practices in a way that is clear and actionable, both during server development and at time of publishing. I have started a discussion about the broader topic: https://github.com/modelcontextprotocol/registry/discussions/635 There is also a fairly detailed document describing the design, architecture, implementation, future plans, etc. See [Enhanced Validation Design](docs/explanations/proposed-enhanced-validation.md) This PR is the first step in the process of improving validation. It adds schema validation and updates all existing validators to use a new model that allows them to track context and return rich and exhaustive results. This has been done in a way that is backward compatible (ValidateServerJSON is unchanged as are all existing validation unit tests). There is a new `mcp-publisher` command called `validate` that is currenty the only place that schema validation and enhanced (exhaustive/rich) validation results are exposed. ### Changes Internal Validation improvements - Schema validation has been implemented and is available as an option in validation methods (defaults to off) - Existing validators track the JSON path (context) of the attribute they're evaluating, passing it to any child validators - Existing validators are exhaustive (return all issues, not failing fast on the first error) - Existing validators return rich validation results, including: - type (schema, semantic, linter) - severity (error, warn, info) - path (JSON path to server.json element) - reference (to the schema element or rule that triggered the result) - message (currently the same as previous error message) A new `validate` command has been added to `mcp-publisher` so publishers can evaluate their server.json before publishing - Includes new schema validation and previous semantic validation - Shows full details of all issues encountered during validation ### Usage Given a server.json that looks like this: ```json { "$schema": "https://static.modelcontextprotocol.io/schemas/2025-09-29/server.schema.json", "name": "io.github.BobDickinson/registry", "description": "An MCP server that provides [describe what your server does]", "repository": { "url": "", "source": "" }, "version": "=1.0.0", "packages": [ { "registryType": "oci", "registryBaseUrl": "https://docker.io", "identifier": "registry", "version": "1.0.0", "transport": { "type": "sse" }, "packageArguments": [ { "type": "named", "name": "--mode", "description": "Operation mode", "format": "foo" } ], "environmentVariables": [ { "description": "Your API key for the service", "isRequired": true, "format": "string", "isSecret": true, "name": "YOUR_API_KEY" } ] } ] } ``` Run the command: `mcp-publisher validate server.json` Which will produce the output: ```bash ❌ Validation failed with 5 issue(s): 1. [error] packages.0.packageArguments.0.format (schema) value must be one of "string", "number", "boolean", "filepath" Reference: #/definitions/Input/properties/format/enum from: [#/definitions/ServerDetail]/properties/packages/items/[#/definitions/Package]/properties/packageArguments/items/[#/definitions/Argument]/else/[#/definitions/NamedArgument]/allOf/0/[#/definitions/InputWithVariables]/allOf/0/[#/definitions/Input]/properties/format/enum 2. [error] packages.0.transport (schema) missing required fields: 'url' Reference: #/definitions/SseTransport/required from: [#/definitions/ServerDetail]/properties/packages/items/[#/definitions/Package]/properties/transport/else/else/[#/definitions/SseTransport]/required 3. [error] repository.url (schema) '' has invalid format 'uri' Reference: #/definitions/Repository/properties/url/format from: [#/definitions/ServerDetail]/properties/repository/[#/definitions/Repository]/properties/url/format 4. [error] version (semantic) version must be a specific version, not a range: "=1.0.0" Reference: version-looks-like-range 5. [error] packages[0].transport.url (semantic) url is required for sse transport type Reference: streamable-transport-url-required Error: validation failed ``` Note in the results above: - All errors contain the JSON path of the triggering element from server.json. - The first three errors are schema errors detected during schema validation. The `Reference` provided contains an absolute path to the schema rule that was violated, followed by the full schema path that enforced that rule (with $ref redirect values substited and enclosed in square brackets). - The error messages provided by the existing semantic validators are exactly the same as the previous error messages those validators produced. In the final solution we would remove semantic validators that are redundant to schema validation (as in number 5 above). We have the option to use the structured data produced by schema validation to replace the generic schema validation message with a more descriptive message if that is an issue (in particular, if the only argument for an ad-hoc validator is that is produces a better/cleaner message, we would just move that message creation code to the schema error result formatter and special case it as opposed to having a redundant validator). ### What's Next If this general direction is supported and this PR is accepted, a fast follow would include: - Add new validators (infliuenced by observed issues) for both semantic errors and best practices - Require passing schema validation (in addition to improved semantic validation) in order to publish - Remove existing validation code that is redundant to schema validation (ensuring error messages remain intelligible) - Update validation client code and tests to handle the new rich return types natively ### Issues Schema validation requires embedding the `server.schema.json` file into the validators package via `go:embed`, which is restricted from embedding files outside of the package. For this reason we copy the schema file into a schema subdir (via a prep target in the makefile) and we .gitignore it. I tried cleaning up the copy in the make clean target, but then the linter would complain about the embed target being missing if it wasn't there during development. I also considered just checking in the schema file and assuming a separate workflow for updating the embedded schema file, but it's not clear what that workflow would be or how it would be maintained. I'm open to a different approach, but the schema file does need to be embedded somehow for schema validation to work. ## How Has This Been Tested? All existing validation tests pass, new tests implemented and all pass. ## Breaking Changes No breaking changes, no behavior change except new `validate` command ## Types of changes <!-- What types of changes does your code introduce? Put an `x` in all the boxes that apply: --> - [ ] 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) - [ ] Documentation update ## Checklist <!-- Go over all the following points, and put an `x` in all the boxes that apply. --> - [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 --------- Co-authored-by: GitHub Action <action@github.com>
478 lines
17 KiB
JSON
478 lines
17 KiB
JSON
{
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"$schema": "http://json-schema.org/draft-07/schema#",
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"$id": "https://static.modelcontextprotocol.io/schemas/2025-09-16/server.schema.json",
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"title": "MCP Server Detail",
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"$ref": "#/definitions/ServerDetail",
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"definitions": {
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"Repository": {
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"type": "object",
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"description": "Repository metadata for the MCP server source code. Enables users and security experts to inspect the code, improving transparency.",
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"required": [
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"url",
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"source"
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],
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"properties": {
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"url": {
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"type": "string",
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"format": "uri",
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"description": "Repository URL for browsing source code. Should support both web browsing and git clone operations.",
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"example": "https://github.com/modelcontextprotocol/servers"
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},
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"source": {
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"type": "string",
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"description": "Repository hosting service identifier. Used by registries to determine validation and API access methods.",
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"example": "github"
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},
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"id": {
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"type": "string",
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"description": "Repository identifier from the hosting service (e.g., GitHub repo ID). Owned and determined by the source forge. Should remain stable across repository renames and may be used to detect repository resurrection attacks - if a repository is deleted and recreated, the ID should change. For GitHub, use: gh api repos/<owner>/<repo> --jq '.id'",
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"example": "b94b5f7e-c7c6-d760-2c78-a5e9b8a5b8c9"
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},
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"subfolder": {
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"type": "string",
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"description": "Optional relative path from repository root to the server location within a monorepo or nested package structure. Must be a clean relative path.",
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"example": "src/everything"
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}
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}
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},
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"Server": {
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"type": "object",
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"required": [
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"name",
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"description",
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"version"
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],
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"properties": {
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"name": {
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"type": "string",
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"description": "Server name in reverse-DNS format. Must contain exactly one forward slash separating namespace from server name.",
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"example": "io.github.user/weather",
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"pattern": "^[a-zA-Z0-9.-]+/[a-zA-Z0-9._-]+$",
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"minLength": 3,
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"maxLength": 200
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},
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"description": {
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"type": "string",
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"description": "Clear human-readable explanation of server functionality. Should focus on capabilities, not implementation details.",
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"example": "MCP server providing weather data and forecasts via OpenWeatherMap API",
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"minLength": 1,
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"maxLength": 100
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},
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"status": {
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"type": "string",
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"enum": ["active", "deprecated", "deleted"],
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"default": "active",
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"description": "Server lifecycle status. 'deprecated' indicates the server is no longer recommended for new usage. 'deleted' indicates the server should never be installed and existing installations should be uninstalled - this is rare, and usually indicates malware or a legal takedown."
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},
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"repository": {
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"$ref": "#/definitions/Repository",
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"description": "Optional repository metadata for the MCP server source code. Recommended for transparency and security inspection."
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},
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"version": {
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"type": "string",
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"maxLength": 255,
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"example": "1.0.2",
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"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. Version ranges are rejected (e.g., '^1.2.3', '~1.2.3', '>=1.2.3', '1.x', '1.*')."
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},
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"websiteUrl": {
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"type": "string",
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"format": "uri",
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"description": "Optional URL to the server's homepage, documentation, or project website. This provides a central link for users to learn more about the server. Particularly useful when the server has custom installation instructions or setup requirements.",
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"example": "https://modelcontextprotocol.io/examples"
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}
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}
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},
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"Package": {
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"type": "object",
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"additionalProperties": false,
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"required": [
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"registryType",
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"identifier",
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"version",
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"transport"
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],
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"properties": {
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"registryType": {
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"type": "string",
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"description": "Registry type indicating how to download packages (e.g., 'npm', 'pypi', 'oci', 'nuget', 'mcpb')",
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"examples": ["npm", "pypi", "oci", "nuget", "mcpb"]
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},
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"registryBaseUrl": {
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"type": "string",
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"format": "uri",
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"description": "Base URL of the package registry",
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"examples": ["https://registry.npmjs.org", "https://pypi.org", "https://docker.io", "https://api.nuget.org", "https://github.com", "https://gitlab.com"]
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},
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"identifier": {
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"type": "string",
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"description": "Package identifier - either a package name (for registries) or URL (for direct downloads)",
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"examples": ["@modelcontextprotocol/server-brave-search", "https://github.com/example/releases/download/v1.0.0/package.mcpb"]
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},
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"version": {
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"type": "string",
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"description": "Package version. Must be a specific version. Version ranges are rejected (e.g., '^1.2.3', '~1.2.3', '>=1.2.3', '1.x', '1.*').",
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"not": {
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"const": "latest"
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},
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"example": "1.0.2",
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"minLength": 1
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},
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"fileSha256": {
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"type": "string",
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"pattern": "^[a-f0-9]{64}$",
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"description": "SHA-256 hash of the package file for integrity verification. Required for MCPB packages and optional for other package types. Authors are responsible for generating correct SHA-256 hashes when creating server.json. If present, MCP clients must validate the downloaded file matches the hash before running packages to ensure file integrity.",
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"example": "fe333e598595000ae021bd27117db32ec69af6987f507ba7a63c90638ff633ce"
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},
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"runtimeHint": {
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"type": "string",
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"description": "A hint to help clients determine the appropriate runtime for the package. This field should be provided when `runtimeArguments` are present.",
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"examples": [
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"npx",
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"uvx",
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"docker",
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"dnx"
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]
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},
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"transport": {
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"anyOf": [
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{
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"$ref": "#/definitions/StdioTransport"
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},
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{
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"$ref": "#/definitions/StreamableHttpTransport"
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},
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{
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"$ref": "#/definitions/SseTransport"
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}
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],
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"description": "Transport protocol configuration for the package"
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},
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"runtimeArguments": {
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"type": "array",
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"description": "A list of arguments to be passed to the package's runtime command (such as docker or npx). The `runtimeHint` field should be provided when `runtimeArguments` are present.",
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"items": {
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"$ref": "#/definitions/Argument"
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}
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},
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"packageArguments": {
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"type": "array",
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"description": "A list of arguments to be passed to the package's binary.",
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"items": {
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"$ref": "#/definitions/Argument"
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}
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},
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"environmentVariables": {
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"type": "array",
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"description": "A mapping of environment variables to be set when running the package.",
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"items": {
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"$ref": "#/definitions/KeyValueInput"
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}
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}
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}
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},
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"Input": {
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"type": "object",
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"properties": {
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"description": {
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"description": "A description of the input, which clients can use to provide context to the user.",
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"type": "string"
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},
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"isRequired": {
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"type": "boolean",
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"default": false
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},
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"format": {
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"type": "string",
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"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.",
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"enum": [
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"string",
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"number",
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"boolean",
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"filepath"
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],
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"default": "string"
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},
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"value": {
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"type": "string",
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"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"
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},
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"isSecret": {
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"type": "boolean",
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"description": "Indicates whether the input is a secret value (e.g., password, token). If true, clients should handle the value securely.",
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"default": false
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},
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"default": {
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"type": "string",
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"description": "The default value for the input."
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},
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"choices": {
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"type": "array",
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"description": "A list of possible values for the input. If provided, the user must select one of these values.",
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"items": {
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"type": "string"
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},
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"example": []
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}
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}
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},
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"InputWithVariables": {
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"allOf": [
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{
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"$ref": "#/definitions/Input"
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},
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{
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"type": "object",
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"properties": {
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"variables": {
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"type": "object",
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"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.",
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"additionalProperties": {
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"$ref": "#/definitions/Input"
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}
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}
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}
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}
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]
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},
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"PositionalArgument": {
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"description": "A positional input is a value inserted verbatim into the command line.",
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"allOf": [
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{
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"$ref": "#/definitions/InputWithVariables"
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},
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{
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"type": "object",
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"required": [
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"type"
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],
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"properties": {
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"type": {
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"type": "string",
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"enum": [
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"positional"
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],
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"example": "positional"
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},
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"valueHint": {
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"type": "string",
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"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.",
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"example": "file_path"
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},
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"isRepeated": {
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"type": "boolean",
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"description": "Whether the argument can be repeated multiple times in the command line.",
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"default": false
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}
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},
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"anyOf": [
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{
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"required": [
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"valueHint"
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]
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},
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{
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"required": [
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"value"
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]
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}
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]
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}
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]
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},
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"NamedArgument": {
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"description": "A command-line `--flag={value}`.",
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"allOf": [
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{
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"$ref": "#/definitions/InputWithVariables"
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},
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{
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"type": "object",
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"required": [
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"type",
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"name"
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],
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"properties": {
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"type": {
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"type": "string",
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"enum": [
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"named"
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],
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"example": "named"
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},
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"name": {
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"type": "string",
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"description": "The flag name, including any leading dashes.",
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"example": "--port"
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},
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"isRepeated": {
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"type": "boolean",
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"description": "Whether the argument can be repeated multiple times.",
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"default": false
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}
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}
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}
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]
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},
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"KeyValueInput": {
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"allOf": [
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{
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"$ref": "#/definitions/InputWithVariables"
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},
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{
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"type": "object",
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"required": [
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"name"
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],
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"properties": {
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"name": {
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"type": "string",
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"description": "Name of the header or environment variable.",
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"example": "SOME_VARIABLE"
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}
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}
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}
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]
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},
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"Argument": {
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"description": "Warning: Arguments construct command-line parameters that may contain user-provided input. This creates potential command injection risks if clients execute commands in a shell environment. For example, a malicious argument value like ';rm -rf ~/Development' could execute dangerous commands. Clients should prefer non-shell execution methods (e.g., posix_spawn) when possible to eliminate injection risks entirely. Where not possible, clients should obtain consent from users or agents to run the resolved command before execution.",
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"anyOf": [
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{
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"$ref": "#/definitions/PositionalArgument"
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},
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{
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"$ref": "#/definitions/NamedArgument"
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}
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]
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},
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"StdioTransport": {
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"type": "object",
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"required": [
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"type"
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],
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"properties": {
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"type": {
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"type": "string",
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"enum": [
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"stdio"
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],
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"description": "Transport type",
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"example": "stdio"
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}
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}
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},
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"StreamableHttpTransport": {
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"type": "object",
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"required": [
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"type",
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"url"
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],
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"properties": {
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"type": {
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"type": "string",
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"enum": [
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"streamable-http"
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],
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"description": "Transport type",
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"example": "streamable-http"
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},
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"url": {
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"type": "string",
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"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.",
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"example": "https://api.example.com/mcp"
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},
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"headers": {
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"type": "array",
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"description": "HTTP headers to include",
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"items": {
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"$ref": "#/definitions/KeyValueInput"
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}
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}
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}
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},
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"SseTransport": {
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"type": "object",
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"required": [
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"type",
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"url"
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],
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"properties": {
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"type": {
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"type": "string",
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"enum": [
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"sse"
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],
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"description": "Transport type",
|
|
"example": "sse"
|
|
},
|
|
"url": {
|
|
"type": "string",
|
|
"format": "uri",
|
|
"description": "Server-Sent Events endpoint URL",
|
|
"example": "https://mcp-fs.example.com/sse"
|
|
},
|
|
"headers": {
|
|
"type": "array",
|
|
"description": "HTTP headers to include",
|
|
"items": {
|
|
"$ref": "#/definitions/KeyValueInput"
|
|
}
|
|
}
|
|
}
|
|
},
|
|
"ServerDetail": {
|
|
"description": "Schema for a static representation of an MCP server. Used in various contexts related to discovery, installation, and configuration.",
|
|
"allOf": [
|
|
{
|
|
"$ref": "#/definitions/Server"
|
|
},
|
|
{
|
|
"type": "object",
|
|
"properties": {
|
|
"$schema": {
|
|
"type": "string",
|
|
"format": "uri",
|
|
"description": "JSON Schema URI for this server.json format",
|
|
"example": "https://static.modelcontextprotocol.io/schemas/2025-09-16/server.schema.json"
|
|
},
|
|
"packages": {
|
|
"type": "array",
|
|
"items": {
|
|
"$ref": "#/definitions/Package"
|
|
}
|
|
},
|
|
"remotes": {
|
|
"type": "array",
|
|
"items": {
|
|
"anyOf": [
|
|
{
|
|
"$ref": "#/definitions/StreamableHttpTransport"
|
|
},
|
|
{
|
|
"$ref": "#/definitions/SseTransport"
|
|
}
|
|
]
|
|
}
|
|
},
|
|
"_meta": {
|
|
"type": "object",
|
|
"description": "Extension metadata using reverse DNS namespacing for vendor-specific data",
|
|
"additionalProperties": true,
|
|
"properties": {
|
|
"io.modelcontextprotocol.registry/publisher-provided": {
|
|
"type": "object",
|
|
"description": "Publisher-provided metadata for downstream registries",
|
|
"additionalProperties": true
|
|
},
|
|
"io.modelcontextprotocol.registry/official": {
|
|
"type": "object",
|
|
"description": "Official MCP registry metadata (read-only, added by registry)",
|
|
"additionalProperties": true
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
]
|
|
}
|
|
}
|
|
}
|