check_license_header

Verify Python files in a git repository contain required license headers in the first five lines, checking for Copyright or SPDX-License-Identifier text without network access or file modifications.

Instructions

Deterministic, network-free, read-only Tier 1 guardian.

Checks .py files tracked by git to ensure the first 5 lines contain "Copyright" OR "SPDX-License-Identifier".

Input Schema

TableJSON Schema

Name	Required	Description	Default
`repo_path`	Yes

Implementation Reference

src/mcp_license_header_guardian/server.py:75-128 (handler)

The implementation of the check_license_header tool which checks if .py files tracked by git contain a copyright notice or SPDX-License-Identifier in the first 5 lines.

def check_license_header(repo_path: str) -> Dict[str, Any]:
    """
    Deterministic, network-free, read-only Tier 1 guardian.

    Checks .py files tracked by git to ensure the first 5 lines contain
    "Copyright" OR "SPDX-License-Identifier".
    """
    if not _repo_path_is_valid(repo_path):
        return _fail_closed("fail-closed: invalid_repo_path", repo_path)

    abs_repo = os.path.abspath(repo_path)

    try:
        tracked = _run_git_ls_files(abs_repo)
    except RuntimeError as e:
        return _fail_closed(f"fail-closed: {str(e)}", repo_path, output={"files_missing_header": [], "notes": ["git ls-files failed"]})

    py_files = [p for p in tracked if p.endswith(".py")]
    missing: List[str] = []

    for rel in py_files:
        full = os.path.join(abs_repo, rel)
        if not _first_n_lines_contains_required_marker(full, n=5):
            missing.append(rel)

    missing.sort()

    output = {
        "files_missing_header": missing,
        "notes": [
            "scope: tracked .py files only",
            "rule: first 5 lines contain Copyright OR SPDX-License-Identifier",
            "listing: git ls-files",
        ],
    }

    if missing:
        return {
            "tool": "check_license_header",
            "repo_path": repo_path,
            "ok": False,
            "fail_closed": True,
            "details": "fail-closed: missing_license_header",
            "output": output,
        }

    return {
        "tool": "check_license_header",
        "repo_path": repo_path,
        "ok": True,
        "fail_closed": False,
        "details": "ok",
        "output": output,
    }

src/mcp_license_header_guardian/server.py:74-74 (registration)
MCP tool registration for check_license_header.
```
@mcp.tool()
```

src/mcp_license_header_guardian/server.py:59-70 (helper)

Helper function that checks if the first N lines of a file contain the required license markers.

def _first_n_lines_contains_required_marker(path: str, n: int = 5) -> bool:
    try:
        with open(path, "rb") as f:
            raw = f.read(8192)
    except Exception:
        return False

    text = raw.decode("utf-8", errors="replace")
    lines = text.splitlines()[:n]
    for line in lines:
        if "Copyright" in line or "SPDX-License-Identifier" in line:
            return True

mcp-license-header-guardian