Api migration

API Migration Skill

This skill enables Claude to automatically migrate code from a deprecated API to a new API. It works with Python and JavaScript/Node.js projects.

How to use this skill

1. Understand the migration scope – ask the user for old/new API names or use default mapping from migration-rules.json.
2. Scan the codebase – run python scripts/scanner.py <path> to get a JSON report of deprecated calls.
3. Apply migrations (via subagents) – replace old calls with new ones, preserving formatting and comments.
4. Validate – run tests or linters; report obstacles.

Files

• migration-rules.json – core mapping old → new.
• regex-patterns.md – regex patterns for detection.
• scripts/scanner.py – executable scanner that outputs JSON.

Example migration

Before (Python):

from old_api import Client
client = Client(api_key="test")
user = client.get_user(user_id=123)

After:

from new_api import Client
client = Client(api_key="test")
user = client.fetch_user_by_id(user_id=123)

Allowed tools

Only read tools plus scanner.py execution. Writing is delegated to subagents with explicit write permissions.

Troubleshooting

• Skill not activating? Check name/description match user request.
• Scanner fails? Ensure Python 3.9+ and re module (built-in).
• No occurrences? Verify regex patterns against actual code.

Progressive Disclosure – Level 3 (Lazy Loading)

This skill supports on-demand loading of additional context to minimize token usage:

• migration-rules.json: Load ONLY when processing a new language or when patterns are unclear.
• regex-patterns.md: Load ONLY if scanner.py returns unexpected results (e.g., false negatives).
• scripts/scanner.py: Executed via Bash – does NOT consume context window.

Loading strategy

if task.language not in cached_rules:
    load("migration-rules.json")
    cache.append(language)
if scanner_results are suspicious or incomplete:
    load("regex-patterns.md")
    re-run scanner with updated patterns