@emcy/openapi-to-mcp

Convert OpenAPI specifications into MCP servers.

Use this package when you want a quick way to turn an OpenAPI spec into a TypeScript MCP server. If you want Emcy Gateway in front of that server, add --use-emcy-gateway.

What it generates

This package generates TypeScript MCP servers.

Most users only need two shapes:

1. standalone_no_auth

   • Public MCP server
   • No built-in upstream auth logic
   • Good for public or already-open APIs

2. standalone_headers

   • Public MCP server
   • Injects static/custom headers into every upstream API request
   • Good for API keys, static bearer tokens, tenant headers, and similar patterns

If you want Emcy Gateway in front of the generated server, opt into the Gateway integration:

• the generated server stays a TypeScript MCP server
• Emcy Gateway owns the public MCP and OAuth edge
• Emcy Host can run the server for you if you want managed hosting

FastMCP and other MCP runtimes can use Emcy Gateway too. This package is only for OpenAPI generation.

The generator no longer produces standalone public OAuth resource servers and no longer supports bearer-token passthrough.

Quick Start

# Standalone MCP server for a public API
npx @emcy/openapi-to-mcp generate \
  --url https://petstore.swagger.io/v2/swagger.json \
  --mode standalone-no-auth

# Standalone MCP server that injects an API key header upstream
npx @emcy/openapi-to-mcp generate \
  --url ./openapi.yaml \
  --name my-api \
  --mode standalone-headers \
  --header X-API-Key=UPSTREAM_API_KEY

# Generate a server and configure it for Emcy Gateway on an OAuth-protected app
npx @emcy/openapi-to-mcp generate \
  --url ./openapi.yaml \
  --name my-app \
  --use-emcy-gateway \
  --gateway-provider sqlos \
  --gateway-auth-server-url https://auth.example.com/sqlos/auth \
  --gateway-client-id todo-mcp-local \
  --gateway-resource https://api.example.com/todos \
  --gateway-scopes "openid profile email offline_access todos.read todos.write"

Installation

Use it directly with npx or install globally:

npm install -g @emcy/openapi-to-mcp

Commands

generate

npx @emcy/openapi-to-mcp generate [options]

| Option | Short | Description | | --- | --- | --- | | --url | -u | URL or file path to OpenAPI spec | | --name | -n | Name for the generated server | | --output | -o | Output directory | | --base-url | -b | Override the upstream API base URL | | --version | | Runtime version string | | --emcy | -e | Include @emcy/sdk telemetry | | --local-sdk | | Use a local @emcy/sdk path | | --prompts-json | | JSON array of MCP prompt definitions | | --tool-instructions-json | | JSON object keyed by tool key for tool-specific AI guidance | | --mode | | Low-level runtime mode. Most users should only pass standalone-no-auth or standalone-headers directly | | --use-emcy-gateway | | Generate a server preconfigured to use Emcy Gateway as the public MCP/OAuth edge | | --header | | Repeatable Header-Name=ENV_VAR mapping for upstream requests | | --gateway-provider | | Emcy Gateway OAuth provider recipe label | | --gateway-auth-server-url | | Downstream authorization server issuer or metadata base URL | | --gateway-client-id | | Downstream client ID Emcy should use | | --gateway-resource | | Downstream API resource / audience | | --gateway-scopes | | Comma or space separated downstream scopes | | --force | -f | Overwrite the output directory |

validate

npx @emcy/openapi-to-mcp validate --url https://api.example.com/openapi.json

Server Modes

standalone_no_auth

Use this when the upstream API is public or already reachable without adding credentials from the MCP runtime.

npx @emcy/openapi-to-mcp generate \
  --url ./openapi.json \
  --mode standalone-no-auth

standalone_headers

Use this when every upstream request needs static headers.

npx @emcy/openapi-to-mcp generate \
  --url ./openapi.json \
  --mode standalone-headers \
  --header X-API-Key=UPSTREAM_API_KEY \
  --header X-Tenant-Id=UPSTREAM_TENANT_ID

If your upstream API needs Authorization: Bearer ..., either:

• model it as a bearer security scheme in the OpenAPI document, or
• pass the full header value through an env var:

npx @emcy/openapi-to-mcp generate \
  --url ./openapi.json \
  --mode standalone-headers \
  --header Authorization=UPSTREAM_AUTHORIZATION

Then set:

UPSTREAM_AUTHORIZATION=Bearer eyJ...

Using Emcy Gateway

Use this when the upstream API is protected by OAuth and you want Emcy Gateway to own the public MCP URL, OAuth flow, and client-facing discovery.

npx @emcy/openapi-to-mcp generate \
  --url ./openapi.json \
  --use-emcy-gateway \
  --gateway-provider sqlos \
  --gateway-auth-server-url https://auth.example.com/sqlos/auth \
  --gateway-client-id todo-mcp-local \
  --gateway-resource https://api.example.com/todos \
  --gateway-scopes "openid profile email offline_access todos.read todos.write"

This is the right mode for apps protected by systems like:

• Auth0
• WorkOS AuthKit
• SqlOS AuthServer/AuthPage
• Entra
• generic OAuth/OIDC authorization servers

Legacy compatibility:

• older --mode emcy-gateway-worker invocations still parse, but --use-emcy-gateway is the supported interface

Typical usage:

1. generate a normal MCP server
2. add --use-emcy-gateway when you want Emcy Gateway to become the public edge for that server

Generated Server

Every generated server includes:

• TypeScript source
• MCP tool bindings for the selected OpenAPI operations
• Streamable HTTP transport
• .env.example
• generated README

Standalone modes also support stdio for desktop clients.

Programmatic Usage

import { parseOpenAPI, mapToMcpTools, generateMcpServer } from "@emcy/openapi-to-mcp";

const parsed = await parseOpenAPI("https://api.example.com/openapi.json");
const tools = mapToMcpTools(parsed.endpoints);

const files = generateMcpServer(
  tools,
  {
    name: "my-api",
    version: "1.0.0",
    baseUrl: "https://api.example.com",
    runtimeMode: "standalone_headers",
    upstreamHeaders: [
      { name: "X-API-Key", envVar: "UPSTREAM_API_KEY" },
    ],
  },
  parsed.securitySchemes
);

Gateway-backed generation:

const files = generateMcpServer(
  tools,
  {
    name: "my-api",
    version: "1.0.0",
    baseUrl: "https://api.example.com",
    gatewayIntegration: {
      provider: "emcy",
      oauth: {
        provider: "sqlos",
        authorizationServerUrl: "https://auth.example.com/sqlos/auth",
        clientId: "todo-mcp-local",
        resource: "https://api.example.com/todos",
        scopes: ["openid", "profile", "todos.read", "todos.write"],
      },
    },
  },
  parsed.securitySchemes
);

What this package does not do

• It does not host a public OAuth authorization server for MCP clients.
• It does not support forwarding end-user bearer tokens from the MCP client to the upstream API.
• It does not try to replace Emcy Host or Emcy Gateway for OAuth-protected apps.

Emcy

Use Emcy when you want to turn an OAuth-protected API into:

• a hosted runtime behind Emcy Host
• a gateway-managed public MCP/OAuth surface
• an embedded agent
• a workspace integration
• an external client surface for tools like VS Code or Claude

The open-source generator handles the runtime. Emcy Host runs it. Emcy Gateway handles the public auth and orchestration layer.

License

MIT © Emcy