Initial project structure for MCP interceptors (#3)

Establishes a multi-language monorepo structure for MCP interceptors
with Python and TypeScript SDKs alongside the existing Go
implementation. Implements an efficient CI/CD system that only tests
what changes.


#### 🏗️ SDK Scaffolding
- **Python SDK** (`python/sdk/`): Modern Python package using
`pyproject.toml`, aligned with official MCP Python SDK patterns
- **TypeScript SDK** (`typescript/sdk/`): ESM-based package structure,
compatible with official MCP TypeScript SDK
- **Monorepo structure**: Consistent `{language}/sdk/` pattern across
all implementations
  
 #### 🚀 CI/CD Pipeline
- **Path-based workflow triggering**: Only runs CI for languages that
actually changed
    - Change Python → only Python CI runs
    - Change multiple languages → only those CIs run
- **Status check workflow**: Single required check that dynamically
validates based on changes
- **Comment triggers**: Maintainers can run all checks with `/test all`
PR comment

typescript/sdk/.eslintrc.json

@@ -0,0 +1,24 @@
+{
+  "root": true,
+  "parser": "@typescript-eslint/parser",
+  "parserOptions": {
+    "ecmaVersion": "latest",
+    "sourceType": "module",
+    "project": "./tsconfig.json"
+  },
+  "plugins": ["@typescript-eslint"],
+  "extends": [
+    "eslint:recommended",
+    "plugin:@typescript-eslint/recommended",
+    "plugin:@typescript-eslint/recommended-requiring-type-checking"
+  ],
+  "env": {
+    "node": true,
+    "es2022": true
+  },
+  "rules": {
+    "@typescript-eslint/explicit-module-boundary-types": "error",
+    "@typescript-eslint/no-explicit-any": "error",
+    "@typescript-eslint/no-unused-vars": ["error", { "argsIgnorePattern": "^_" }]
+  }
+}

typescript/sdk/.nvmrc

@@ -0,0 +1 @@
+20

typescript/sdk/README.md

@@ -0,0 +1,40 @@
+# MCP Interceptors TypeScript SDK
+
+TypeScript implementation of the Model Context Protocol (MCP) interceptor framework.
+
+## Installation
+
+```bash
+npm install @ext-modelcontextprotocol/interceptors
+```
+
+## Usage
+
+```typescript
+import { Interceptor } from '@ext-modelcontextprotocol/interceptors';
+
+// The MCP SDK is available as a peer dependency
+import { Client, Server } from '@modelcontextprotocol/sdk';
+
+// Example usage will be added as the implementation progresses
+```
+
+## Development
+
+```bash
+# Install dependencies
+npm install
+
+# Build
+npm run build
+
+# Run tests
+npm test
+
+# Lint
+npm run lint
+```
+
+## License
+
+Apache License 2.0 - See LICENSE file in the root directory for details.

typescript/sdk/package.json

@@ -0,0 +1,56 @@
+{
+  "name": "@ext-modelcontextprotocol/interceptors",
+  "version": "0.1.0",
+  "description": "TypeScript SDK for Model Context Protocol interceptors",
+  "type": "module",
+  "exports": {
+    ".": {
+      "types": "./dist/index.d.ts",
+      "import": "./dist/index.js"
+    }
+  },
+  "main": "./dist/index.js",
+  "types": "./dist/index.d.ts",
+  "engines": {
+    "node": ">=20"
+  },
+  "scripts": {
+    "build": "tsc",
+    "test": "vitest run",
+    "test:watch": "vitest",
+    "lint": "eslint src --ext .ts",
+    "prepublishOnly": "npm run build"
+  },
+  "keywords": [
+    "mcp",
+    "model-context-protocol",
+    "interceptors"
+  ],
+  "author": "The MCP Interceptors Authors",
+  "license": "Apache-2.0",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/modelcontextprotocol/ext-interceptors.git",
+    "directory": "typescript/sdk"
+  },
+  "bugs": {
+    "url": "https://github.com/modelcontextprotocol/ext-interceptors/issues"
+  },
+  "homepage": "https://github.com/modelcontextprotocol/ext-interceptors",
+  "files": [
+    "dist",
+    "src",
+    "README.md"
+  ],
+  "peerDependencies": {
+    "@modelcontextprotocol/sdk": "^1.0.0"
+  },
+  "devDependencies": {
+    "@types/node": "^20.0.0",
+    "@typescript-eslint/eslint-plugin": "^6.0.0",
+    "@typescript-eslint/parser": "^6.0.0",
+    "eslint": "^8.0.0",
+    "typescript": "^5.0.0",
+    "vitest": "^2.0.0"
+  }
+}

typescript/sdk/src/index.ts

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+// Copyright 2025 The MCP Interceptors Authors. All rights reserved.
+// Use of this source code is governed by a Apache-2.0
+// license that can be found in the LICENSE file.
+
+/**
+ * MCP Interceptors TypeScript SDK
+ *
+ * Implements MCP Interceptors based on SEP-1763:
+ * https://github.com/modelcontextprotocol/modelcontextprotocol/issues/1763
+ */
+
+export * from './interceptors.js';

typescript/sdk/src/interceptors.test.ts

@@ -0,0 +1,11 @@
+// Copyright 2025 The MCP Interceptors Authors. All rights reserved.
+// Use of this source code is governed by a Apache-2.0
+// license that can be found in the LICENSE file.
+
+import { describe, it, expect } from 'vitest';
+
+describe('Interceptors', () => {
+  it('should be defined', () => {
+    expect(true).toBe(true);
+  });
+});

typescript/sdk/src/interceptors.ts

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+// Copyright 2025 The MCP Interceptors Authors. All rights reserved.
+// Use of this source code is governed by a Apache-2.0
+// license that can be found in the LICENSE file.
+
+/**
+ * Core interceptor functionality for MCP
+ *
+ * Based on SEP-1763:
+ * https://github.com/modelcontextprotocol/modelcontextprotocol/issues/1763
+ */
+
+// Placeholder for interceptor implementation

typescript/sdk/tsconfig.json

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+{
+  "compilerOptions": {
+    "target": "esnext",
+    "module": "NodeNext",
+    "lib": ["esnext"],
+    "outDir": "./dist",
+    "rootDir": "./src",
+    "declaration": true,
+    "declarationMap": true,
+    "sourceMap": true,
+    "strict": true,
+    "isolatedModules": true,
+    "esModuleInterop": true,
+    "allowSyntheticDefaultImports": true,
+    "skipLibCheck": true,
+    "forceConsistentCasingInFileNames": true,
+    "moduleResolution": "NodeNext",
+    "resolveJsonModule": true
+  },
+  "include": ["src/**/*"],
+  "exclude": ["node_modules", "dist"]
+}

typescript/sdk/vitest.config.js

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+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    globals: true,
+    environment: 'node',
+    include: ['src/**/*.test.ts', 'test/**/*.test.ts'],
+    exclude: ['**/node_modules/**', '**/dist/**']
+  }
+});