API Integration Patterns Skill

Standardized patterns for integrating external APIs and CLI tools in the autonomous-dev plugin ecosystem. Focuses on safety, reliability, and security when calling external services.

When This Skill Activates

• Integrating external APIs (GitHub, etc.)
• Executing subprocess commands safely
• Implementing retry logic
• Handling authentication
• Managing rate limits
• Keywords: "api", "subprocess", "github", "gh cli", "retry", "authentication"

---

Core Patterns

1. Subprocess Safety (CWE-78 Prevention)

Definition: Execute external commands safely without command injection vulnerabilities.

Critical Rules:

• ✅ ALWAYS use argument arrays: ["gh", "issue", "create"]
• ❌ NEVER use shell=True with user input
• ✅ ALWAYS whitelist allowed commands
• ✅ ALWAYS set timeouts

Pattern:

import subprocess
from typing import List

def safe_subprocess(
    command: List[str],
    *,
    allowed_commands: List[str],
    timeout: int = 30
) -> subprocess.CompletedProcess:
    """Execute subprocess with CWE-78 prevention.

    Args:
        command: Command and arguments as list (NOT string!)
        allowed_commands: Whitelist of allowed commands
        timeout: Maximum execution time in seconds

    Returns:
        Completed subprocess result

    Raises:
        SecurityError: If command not in whitelist
        subprocess.TimeoutExpired: If timeout exceeded

    Security:
        - CWE-78 Prevention: Argument arrays (no shell injection)
        - Command Whitelist: Only approved commands
        - Timeout: DoS prevention

    Example:
        >>> result = safe_subprocess(
        ...     ["gh", "issue", "create", "--title", user_title],
        ...     allowed_commands=["gh", "git"]
        ... )
    """
    # Whitelist validation
    if command[0] not in allowed_commands:
        raise SecurityError(f"Command not allowed: {command[0]}")

    # Execute with argument array (NEVER shell=True!)
    return subprocess.run(
        command,
        capture_output=True,
        text=True,
        timeout=timeout,
        check=True,
        shell=False  # CRITICAL
    )

See: docs/subprocess-safety.md, examples/safe-subprocess-example.py

---

2. GitHub CLI (gh) Integration

Definition: Standardized patterns for GitHub operations via gh CLI.

Pattern:

def create_github_issue(
    title: str,
    body: str,
    *,
    labels: Optional[List[str]] = None,
    timeout: int = 30
) -> str:
    """Create GitHub issue using gh CLI.

    Args:
        title: Issue title
        body: Issue body (markdown)
        labels: Issue labels (default: None)
        timeout: Command timeout in seconds

    Returns:
        Issue URL

    Raises:
        subprocess.CalledProcessError: If gh command fails
        RuntimeError: If gh CLI not installed

    Example:
        >>> url = create_github_issue(
        ...     "Bug: Login fails",
        ...     "Login button doesn't work",
        ...     labels=["bug", "p1"]
        ... )
    """
    # Build gh command (argument array)
    cmd = ["gh", "issue", "create", "--title", title, "--body", body]

    if labels:
        for label in labels:
            cmd.extend(["--label", label])

    # Execute safely
    result = subprocess.run(
        cmd,
        capture_output=True,
        text=True,
        timeout=timeout,
        check=True,
        shell=False
    )

    # Extract URL from output
    return result.stdout.strip()

See: docs/github-cli-integration.md, examples/github-issue-example.py

---

3. Retry Logic with Exponential Backoff

Definition: Automatically retry failed API calls with exponential backoff.

Pattern:

import time
from typing import Callable, TypeVar, Any

T = TypeVar('T')

def retry_with_backoff(
    func: Callable[..., T],
    *,
    max_attempts: int = 3,
    base_delay: float = 1.0,
    max_delay: float = 60.0
) -> T:
    """Retry function with exponential backoff.

    Args:
        func: Function to retry
        max_attempts: Maximum retry attempts
        base_delay: Initial delay in seconds
        max_delay: Maximum delay in seconds

    Returns:
        Function result

    Raises:
        Exception: Last exception if all retries fail

    Example:
        >>> result = retry_with_backoff(
        ...     lambda: api_call(),
        ...     max_attempts=5,
        ...     base_delay=2.0
        ... )
    """
    last_exception = None

    for attempt in range(max_attempts):
        try:
            return func()
        except Exception as e:
            last_exception = e

            if attempt < max_attempts - 1:
                # Exponential backoff: 1s, 2s, 4s, 8s, ...
                delay = min(base_delay * (2 ** attempt), max_delay)
                time.sleep(delay)

    raise last_exception

See: docs/retry-logic.md, templates/retry-decorator-template.py

---

4. Authentication Patterns

Definition: Secure handling of API credentials and tokens.

Principles:

• Use environment variables for credentials
• Never hardcode API keys
• Never log credentials
• Validate credentials before use

Pattern:

import os
from typing import Optional

def get_github_token() -> str:
    """Get GitHub token from environment.

    Returns:
        GitHub personal access token

    Raises:
        RuntimeError: If token not found

    Security:
        - Environment Variables: Never hardcode tokens
        - Validation: Check token format
        - No Logging: Never log credentials
    """
    token = os.getenv("GITHUB_TOKEN")

    if not token:
        raise RuntimeError(
            "GITHUB_TOKEN not found in environment\n"
            "Set with: export GITHUB_TOKEN=your_token\n"
            "Or add to .env file"
        )

    # Validate token format (basic check)
    if not token.startswith("ghp_") and not token.startswith("github_pat_"):
        raise ValueError("Invalid GitHub token format")

    return token

See: docs/authentication-patterns.md, templates/github-api-template.py

---

5. Rate Limiting and Quota Management

Definition: Handle API rate limits gracefully.

Pattern:

import time
from datetime import datetime, timedelta

class RateLimiter:
    """Simple rate limiter for API calls.

    Attributes:
        max_calls: Maximum calls per window
        window_seconds: Time window in seconds
    """

    def __init__(self, max_calls: int, window_seconds: int):
        self.max_calls = max_calls
        self.window_seconds = window_seconds
        self.calls = []

    def wait_if_needed(self) -> None:
        """Wait if rate limit would be exceeded."""
        now = datetime.now()
        cutoff = now - timedelta(seconds=self.window_seconds)

        # Remove old calls outside window
        self.calls = [c for c in self.calls if c > cutoff]

        # Wait if at limit
        if len(self.calls) >= self.max_calls:
            oldest = self.calls[0]
            wait_until = oldest + timedelta(seconds=self.window_seconds)
            wait_seconds = (wait_until - now).total_seconds()

            if wait_seconds > 0:
                time.sleep(wait_seconds)

            # Retry removal after wait
            self.calls = [c for c in self.calls if c > cutoff]

        # Record this call
        self.calls.append(now)

See: docs/rate-limiting.md, examples/github-api-example.py

---

Usage Guidelines

For Library Authors

When integrating external APIs:

1. Use subprocess safely with argument arrays
2. Whitelist commands to prevent injection
3. Add retry logic for transient failures
4. Handle authentication securely via environment
5. Respect rate limits to avoid quota exhaustion

For Claude

When creating API integrations:

1. Load this skill when keywords match
2. Follow safety patterns for subprocess
3. Implement retries for reliability
4. Reference templates for common patterns

Token Savings

By centralizing API integration patterns:

• Before: ~45 tokens per library for subprocess safety docs
• After: ~10 tokens for skill reference
• Savings: ~35 tokens per library
• Total: ~280 tokens across 8 libraries (3-4% reduction)

---

Progressive Disclosure

This skill uses Claude Code 2.0+ progressive disclosure architecture:

• Metadata (frontmatter): Always loaded (~170 tokens)
• Full content: Loaded only when keywords match
• Result: Efficient context usage

---

Templates and Examples

Templates

• templates/subprocess-executor-template.py: Safe subprocess execution
• templates/retry-decorator-template.py: Retry logic decorator
• templates/github-api-template.py: GitHub API integration

Examples

• examples/github-issue-example.py: Issue creation via gh CLI
• examples/github-pr-example.py: PR creation patterns
• examples/safe-subprocess-example.py: Command execution safety

Documentation

• docs/subprocess-safety.md: CWE-78 prevention
• docs/github-cli-integration.md: gh CLI patterns
• docs/retry-logic.md: Retry strategies
• docs/authentication-patterns.md: Credential handling

---

Cross-References

This skill integrates with other autonomous-dev skills:

• library-design-patterns: Security-first design
• security-patterns: CWE-78 prevention
• error-handling-patterns: Retry and recovery

---

Maintenance

Update when:

• New API integration patterns emerge
• Security best practices evolve
• gh CLI adds new features

Last Updated: 2025-11-16 (Phase 8.8 - Initial creation) Version: 1.0.0