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

python/sdk/README.md

@@ -0,0 +1,31 @@
+# MCP Interceptors Python SDK
+
+Python implementation of the Model Context Protocol (MCP) interceptor framework.
+
+## Installation
+
+```bash
+pip install mcp-ext-interceptors
+```
+
+## Usage
+
+```python
+from mcp_ext_interceptors import Interceptor
+
+# Example usage will be added as the implementation progresses
+```
+
+## Development
+
+```bash
+# Install in development mode
+pip install -e .
+
+# Run tests (when available)
+pytest
+```
+
+## License
+
+Apache License 2.0 - See LICENSE file in the root directory for details.

python/sdk/pyproject.toml

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+[project]
+name = "mcp-ext-interceptors"
+version = "0.1.0"
+description = "Python SDK for Model Context Protocol interceptors"
+authors = [{name = "The MCP Interceptors Authors"}]
+readme = "README.md"
+license = {text = "Apache-2.0"}
+requires-python = ">=3.10"
+classifiers = [
+    "Development Status :: 3 - Alpha",
+    "Intended Audience :: Developers",
+    "License :: OSI Approved :: Apache Software License",
+    "Programming Language :: Python :: 3",
+    "Programming Language :: Python :: 3.10",
+    "Programming Language :: Python :: 3.11",
+    "Programming Language :: Python :: 3.12",
+]
+dependencies = [
+    "mcp>=1.0.0",
+]
+
+[project.urls]
+"Homepage" = "https://github.com/modelcontextprotocol/ext-interceptors"
+"Bug Reports" = "https://github.com/modelcontextprotocol/ext-interceptors/issues"
+"Source" = "https://github.com/modelcontextprotocol/ext-interceptors"
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[tool.hatch.build.targets.wheel]
+packages = ["src/mcp_ext_interceptors"]
+
+[tool.ruff]
+line-length = 120
+target-version = "py310"
+
+[tool.ruff.lint]
+select = [
+    "E",      # pycodestyle
+    "F",      # pyflakes
+    "I",      # isort
+    "UP",     # pyupgrade
+    "C4",     # flake8-comprehensions
+    "PERF",   # Perflint
+]
+
+[tool.ruff.lint.per-file-ignores]
+"__init__.py" = ["F401"]  # Allow unused imports in __init__.py
+
+[tool.ruff.format]
+quote-style = "double"
+indent-style = "space"
+
+[tool.mypy]
+python_version = "3.10"
+warn_return_any = true
+warn_unused_configs = true
+disallow_untyped_defs = true
+ignore_missing_imports = true
+
+[tool.pyright]
+typeCheckingMode = "basic"
+include = ["src/mcp_ext_interceptors", "tests"]
+venvPath = "."
+venv = ".venv"
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]
+python_files = ["test_*.py", "*_test.py"]
+addopts = "--strict-markers --verbose"

python/sdk/src/mcp_ext_interceptors/__init__.py

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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 Python SDK
+
+Implements MCP Interceptors based on SEP-1763:
+https://github.com/modelcontextprotocol/modelcontextprotocol/issues/1763
+"""

python/sdk/src/mcp_ext_interceptors/interceptor.py

@@ -0,0 +1,8 @@
+# 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.
+
+"""
+Package interceptors implements MCP Interceptors based on SEP-1763:
+https://github.com/modelcontextprotocol/modelcontextprotocol/issues/1763
+"""

python/sdk/src/mcp_ext_interceptors/py.typed

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+# Marker file for PEP 561
+# This file indicates that this package supports type checking

python/sdk/tests/__init__.py

@@ -0,0 +1 @@
+# Tests for mcp-ext-interceptors

python/sdk/tests/test_interceptors.py

@@ -0,0 +1,10 @@
+# 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.
+
+"""Tests for MCP interceptors."""
+
+
+def test_placeholder():
+    """Placeholder test to ensure pytest runs successfully."""
+    assert True