MCP OpenAPI Schema Explorer

An MCP (Model Context Protocol) server that provides token-efficient access to OpenAPI (v3.0) and Swagger (v2.0) specifications via MCP Resources.

Project Goal

The primary goal of this project is to allow MCP clients (like Cline or Claude Desktop) to explore the structure and details of large OpenAPI specifications without needing to load the entire file into an LLM's context window. It achieves this by exposing parts of the specification through MCP Resources, which are well-suited for read-only data exploration.

This server supports loading specifications from both local file paths and remote HTTP/HTTPS URLs. Swagger v2.0 specifications are automatically converted to OpenAPI v3.0 upon loading.

Why MCP Resources?

The Model Context Protocol defines both Resources and Tools.

• Resources: Represent data sources (like files, API responses). They are ideal for read-only access and exploration by MCP clients (e.g., browsing API paths in Claude Desktop).
• Tools: Represent executable actions or functions, often used by LLMs to perform tasks or interact with external systems.

While other MCP servers exist that provide access to OpenAPI specs via Tools, this project specifically focuses on providing access via Resources. This makes it particularly useful for direct exploration within MCP client applications.

For more details on MCP clients and their capabilities, see the MCP Client Documentation.

Usage with MCP Clients (Recommended)

This server is designed to be run by MCP clients. The recommended way to configure it is using npx, which downloads and runs the package without requiring a global installation.

Example Configuration (Claude Desktop - claude_desktop_config.json):

{
  "mcpServers": {
    "My API Spec": {
      "command": "npx",
      "args": [
        "-y",
        "mcp-openapi-schema-explorer",
        "/path/to/your/local/openapi.json",
        "--output-format",
        "yaml"
      ],
      "env": {}
    }
  }
}

Configuration Details:

• "My API Spec": Choose a descriptive name for this server instance. This is how you'll identify it within your MCP client.
• command: Use "npx" to run the package directly.
• args:
  • "-y": Auto-confirms the npx installation prompt if needed the first time.
  • "mcp-openapi-schema-explorer": The name of the package to execute.
  • "/path/to/your/local/openapi.json": Required. The absolute path to your local spec file or the full URL to a remote spec (e.g., "https://remote/url/spec.json").
  • "--output-format", "yaml": Optional. Specifies the output format for detailed resource views. Defaults to "json". Other options are "yaml" and "json-minified".
• env: Currently, no environment variables are needed for this server.

Notes:

• This server handles one specification per instance. To explore multiple specifications simultaneously, configure multiple entries under mcpServers in your client's configuration file, each pointing to a different spec file or URL and using a unique server name.

Usage with Docker

As an alternative to npx or global installation, you can run the server using Docker. The official image is available on Docker Hub: kadykov/mcp-openapi-schema-explorer.

Running the Container:

The container expects the path or URL to the OpenAPI specification as a command-line argument, similar to the npx usage.

• Remote URL: Pass the URL directly to docker run.

  docker run --rm -i kadykov/mcp-openapi-schema-explorer:latest https://petstore3.swagger.io/api/v3/openapi.json

• Local File: Mount the local file into the container using the -v flag and provide the path inside the container as the argument.

  # Example: Mount local file ./my-spec.yaml to /spec/api.yaml inside the container
  docker run --rm -i -v "$(pwd)/my-spec.yaml:/spec/api.yaml" kadykov/mcp-openapi-schema-explorer:latest /spec/api.yaml

  (Note: Replace $(pwd)/my-spec.yaml with the actual path to your local file)

• Output Format: You can still use the --output-format flag:

  docker run --rm -i kadykov/mcp-openapi-schema-explorer:latest https://petstore3.swagger.io/api/v3/openapi.json --output-format yaml

Example MCP Client Configuration (Docker):

Here's how you might configure this in a client like Claude Desktop (claude_desktop_config.json):

• Using a Remote URL:

  {
    "mcpServers": {
      "My API Spec (Docker Remote)": {
        "command": "docker",
        "args": [
          "run",
          "--rm",
          "-i",
          "kadykov/mcp-openapi-schema-explorer:latest",
          "https://petstore3.swagger.io/api/v3/openapi.json"
        ],
        "env": {}
      }
    }
  }

• Using a Local File:

  {
    "mcpServers": {
      "My API Spec (Docker Local)": {
        "command": "docker",
        "args": [
          "run",
          "--rm",
          "-i",
          "-v",
          "/full/path/to/your/local/openapi.yaml:/spec/api.yaml",
          "kadykov/mcp-openapi-schema-explorer:latest",
          "/spec/api.yaml",
          "--output-format",
          "yaml"
        ],
        "env": {}
      }
    }
  }

  (Remember to replace /full/path/to/your/local/openapi.yaml with the correct absolute path on your host machine)

Alternative: Global Installation (Less Common)

If you prefer, you can install the server globally:

npm install -g mcp-openapi-schema-explorer

If installed globally, your MCP client configuration would change:

• command: Likely mcp-openapi-schema-explorer (or the full path if needed).
• args: Would only contain the <path-or-url-to-spec> and optional --output-format flag (omit npx and -y).

Features

• MCP Resource Access: Explore OpenAPI specs via intuitive URIs (openapi://info, openapi://paths/..., openapi://components/...).
• OpenAPI v3.0 & Swagger v2.0 Support: Loads both formats, automatically converting v2.0 to v3.0.
• Local & Remote Files: Load specs from local file paths or HTTP/HTTPS URLs.
• Token-Efficient: Designed to minimize token usage for LLMs by providing structured access.
• Multiple Output Formats: Get detailed views in JSON (default), YAML, or minified JSON (--output-format).
• Dynamic Server Name: Server name in MCP clients reflects the info.title from the loaded spec.
• Reference Transformation: Internal $refs (#/components/...) are transformed into clickable MCP URIs.

Available MCP Resources

This server exposes the following MCP resource templates for exploring the OpenAPI specification.

Understanding Multi-Value Parameters (*)

Some resource templates include parameters ending with an asterisk (*), like {method*} or {name*}. This indicates that the parameter accepts multiple comma-separated values. For example, to request details for both the GET and POST methods of a path, you would use a URI like openapi://paths/users/get,post. This allows fetching details for multiple items in a single request.

Resource Templates:

• openapi://{field}

  • Description: Accesses top-level fields of the OpenAPI document (e.g., info, servers, tags) or lists the contents of paths or components. The specific available fields depend on the loaded specification.
  • Example: openapi://info
  • Output: text/plain list for paths and components; configured format (JSON/YAML/minified JSON) for other fields.
  • Completions: Provides dynamic suggestions for {field} based on the actual top-level keys found in the loaded spec.

• openapi://paths/{path}

  • Description: Lists the available HTTP methods (operations) for a specific API path.
  • Parameter: {path} - The API path string. Must be URL-encoded (e.g., /users/{id} becomes users%2F%7Bid%7D).
  • Example: openapi://paths/users%2F%7Bid%7D
  • Output: text/plain list of methods.
  • Completions: Provides dynamic suggestions for {path} based on the paths found in the loaded spec (URL-encoded).

• openapi://paths/{path}/{method*}

  • Description: Gets the detailed specification for one or more operations (HTTP methods) on a specific API path.
  • Parameters:
    • {path} - The API path string. Must be URL-encoded.
    • {method*} - One or more HTTP methods (e.g., get, post, get,post). Case-insensitive.
  • Example (Single): openapi://paths/users%2F%7Bid%7D/get
  • Example (Multiple): openapi://paths/users%2F%7Bid%7D/get,post
  • Output: Configured format (JSON/YAML/minified JSON).
  • Completions: Provides dynamic suggestions for {path}. Provides static suggestions for {method*} (common HTTP verbs like GET, POST, PUT, DELETE, etc.).

• openapi://components/{type}

  • Description: Lists the names of all defined components of a specific type (e.g., schemas, responses, parameters). The specific available types depend on the loaded specification. Also provides a short description for each listed type.
  • Example: openapi://components/schemas
  • Output: text/plain list of component names with descriptions.
  • Completions: Provides dynamic suggestions for {type} based on the component types found in the loaded spec.

• openapi://components/{type}/{name*}

  • Description: Gets the detailed specification for one or more named components of a specific type.
  • Parameters:
    • {type} - The component type.
    • {name*} - One or more component names (e.g., User, Order, User,Order). Case-sensitive.
  • Example (Single): openapi://components/schemas/User
  • Example (Multiple): openapi://components/schemas/User,Order
  • Output: Configured format (JSON/YAML/minified JSON).
  • Completions: Provides dynamic suggestions for {type}. Provides dynamic suggestions for {name*} only if the loaded spec contains exactly one component type overall (e.g., only schemas). This limitation exists because the MCP SDK currently doesn't support providing completions scoped to the selected {type}; providing all names across all types could be misleading.

Contributing

Contributions are welcome! Please see the CONTRIBUTING.md file for guidelines on setting up the development environment, running tests, and submitting changes.

Releases

This project uses semantic-release for automated version management and package publishing based on Conventional Commits.

Future Plans

(Future plans to be determined)