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Agent skill

Migrating APIs

by jeremylongshore in jeremylongshore/tons-of-skills-marketplace

Implement API migrations between versions, platforms, or frameworks with minimal downtime.

MITAuto-check passedDatabases

Install Migrating APIs

skills CLI
$ npx skills add jeremylongshore/tons-of-skills-marketplace --skill migrating-apis -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install jeremylongshore/tons-of-skills-marketplace migrating-apis --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/jeremylongshore/tons-of-skills-marketplace.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/.curated/migrating-apis .claude/skills/migrating-apis && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
migrating-apis
GitHub stars
2.8k
Token cost
~1.4k tokens
SKILL.md length
601 words
Files
4 (incl. references)
Skills in repo
3,342
Repo updated
First seen
Licence
MIT

At a glance

Implement API migrations between versions, platforms, or frameworks with minimal downtime.

  • Works in 8 steps: Inventory all existing endpoints using… → Generate an endpoint mapping table that… → Create request/response adapters that… → …
  • Upgrading APIs between versions
  • SKILL.md covers Overview, Prerequisites, Instructions and Output, plus 3 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Migrating APIs is an agent skill from jeremylongshore/tons-of-skills-marketplace. Implement API migrations between versions, platforms, or frameworks with minimal downtime. Use when upgrading APIs between versions. Trigger with phrases like "migrate the API", "upgrade API version", or "migrate to new API".

Its SKILL.md is about 1.4k tokens, which your agent loads only when the skill is triggered. The skill folder holds 4 other files, including reference files (for example `references/errors.md`, `references/examples.md` and `references/implementation.md`). Compatibility notes: Designed for Claude Code

It sits in Databases. The repository describes itself as: Model-agnostic agent-skills platform with a harness-free canonical layer, verified adapters, and the ccpi package manager. Explore at tonsofskills.com. The licence is MIT.

When your agent uses it

  • Upgrading APIs between versions
  • With phrases like migrate the API
  • Upgrade API version
  • Migrate to new API

Example prompts

  • “migrate the API”
  • “upgrade API version”
  • “migrate to new API”
  • “/migrating-apis”

Requirements

  • Python 3
  • Node.js
  • Compatibility (from SKILL.md): Designed for Claude Code
  • Pre-approved tools (allowed-tools): Read, Write, Edit, Grep, Glob, Bash(api:migrate-*)

Workflow steps

8 steps, taken from the first numbered list in SKILL.md.

  1. Inventory all existing endpoints using Grep and Read, documenting HTTP methods, URL patterns, request/response schemas, authentication…
  2. Generate an endpoint mapping table that pairs each legacy endpoint with its target equivalent, flagging breaking changes in URL structure…
  3. Create request/response adapters that transform legacy format to target format, handling field renames, nested-to-flat conversions, and…
  4. Implement a traffic router (reverse proxy rules or middleware) that directs requests to either the legacy or target implementation based…
  5. Set up traffic shadowing to duplicate production requests to the target implementation without serving target responses, comparing outputs…
  6. Build a migration dashboard tracking per-endpoint migration status (legacy-only, shadow, canary, migrated), error rates, and latency…
  7. Execute phased cutover: shadow (compare only) -> canary (1% traffic to target) -> gradual ramp (10%, 25%, 50%, 100%) -> legacy…
  8. Validate migration completeness by running the full integration test suite against the target implementation and comparing response bodies…

What it can do on your machine

Read from SKILL.md and the folder at commit cfae287. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves these tools, so the agent can use them without asking each time:

    • Read
    • Write
    • Edit
    • Grep
    • Glob
    • Bash(api:migrate-*)

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md.

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

  • Compatibility

    Designed for Claude Code

    From compatibility in the SKILL.md frontmatter.

Context cost

Migrating APIs loads about 1.4k tokens when it runs, and up to ~3.2k if it reads all its reference files. Until then it costs about 60 tokens; SKILL.md has 601 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~60
When it runs · the whole SKILL.md, loaded when a task matches
~1.4k
With references · SKILL.md plus every file in references/, read only if the agent opens them
~3.2k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from jeremylongshore/tons-of-skills-marketplace at commit cfae287, republished under its MIT licence (© jeremylongshore). 601 words, ~1,386 tokens.

Download SKILL.mdSave it as .claude/skills/migrating-apis/SKILL.md (or your agent's skills folder). This skill also uses 3 other files; get the full folder from GitHub.
name
migrating-apis
description
Implement API migrations between versions, platforms, or frameworks with minimal downtime. Use when upgrading APIs between versions. Trigger with phrases like "migrate the API", "upgrade API version", or "migrate to new API".
allowed-tools
Read, Write, Edit, Grep, Glob, Bash(api:migrate-*)
compatibility
Designed for Claude Code
version
1.25.0
author
Jeremy Longshore <jeremy@intentsolutions.io>
license
MIT
tags
api, migration, migrating-apis

Migrating APIs

Overview

Implement API migrations between versions, frameworks, or platforms with minimal downtime using strangler fig pattern, parallel running, and traffic shadowing. Generate migration plans that map old endpoints to new equivalents, transform request/response formats, and validate data consistency between legacy and target implementations.

Prerequisites

  • Source API codebase and OpenAPI specification accessible for analysis
  • Target framework or platform environment provisioned and accessible
  • Traffic routing capability for gradual cutover (reverse proxy, feature flags, or API gateway)
  • Database migration tools if schema changes accompany the API migration (Flyway, Alembic, Prisma Migrate)
  • Integration test suite covering all existing API consumers

Instructions

  1. Inventory all existing endpoints using Grep and Read, documenting HTTP methods, URL patterns, request/response schemas, authentication mechanisms, and consumer dependencies.
  2. Generate an endpoint mapping table that pairs each legacy endpoint with its target equivalent, flagging breaking changes in URL structure, field names, data types, and authentication flow.
  3. Create request/response adapters that transform legacy format to target format, handling field renames, nested-to-flat conversions, and enum value changes.
  4. Implement a traffic router (reverse proxy rules or middleware) that directs requests to either the legacy or target implementation based on migration phase, endpoint, or feature flag.
  5. Set up traffic shadowing to duplicate production requests to the target implementation without serving target responses, comparing outputs for data consistency validation.
  6. Build a migration dashboard tracking per-endpoint migration status (legacy-only, shadow, canary, migrated), error rates, and latency comparison between implementations.
  7. Execute phased cutover: shadow (compare only) -> canary (1% traffic to target) -> gradual ramp (10%, 25%, 50%, 100%) -> legacy decommission, with automatic rollback triggers.
  8. Validate migration completeness by running the full integration test suite against the target implementation and comparing response bodies with legacy for a representative request sample.

See ${CLAUDE_SKILL_DIR}/references/implementation.md for the full implementation guide.

Output

  • ${CLAUDE_SKILL_DIR}/migration/endpoint-mapping.json - Legacy-to-target endpoint mapping with change annotations
  • ${CLAUDE_SKILL_DIR}/migration/adapters/ - Request/response transformation functions per endpoint
  • ${CLAUDE_SKILL_DIR}/migration/router.js - Traffic routing middleware with phase-based switching
  • ${CLAUDE_SKILL_DIR}/migration/shadow-compare.js - Traffic shadow comparison and diff reporting
  • ${CLAUDE_SKILL_DIR}/migration/dashboard.md - Migration progress tracking per endpoint
  • ${CLAUDE_SKILL_DIR}/tests/migration/ - Parity tests comparing legacy and target responses
Show full SKILL.md (263 more words)Show less

Error Handling

ErrorCauseSolution
Response mismatch in shadowTarget returns different data than legacy for same requestLog diff details; classify as expected (intentional change) or bug; fix before canary phase
Adapter transformation failureLegacy request contains edge-case field values not handled by adapterAdd fallback handling; log unmatched fields; expand adapter test coverage
Rollback triggeredCanary error rate exceeds threshold (e.g., >2% 5xx)Automatically route traffic back to legacy; alert migration team; analyze failures
Consumer authentication breakTarget uses different auth scheme than legacyRun auth adapter translating legacy tokens to target format during transition
Data inconsistencyDatabase schema migration introduced transformation errorsRun data validation queries comparing legacy and target data stores; fix transformation logic

Refer to ${CLAUDE_SKILL_DIR}/references/errors.md for comprehensive error patterns.

Examples

Express to FastAPI migration: Migrate a Node.js Express API to Python FastAPI, using nginx as the traffic router, shadowing production traffic for 1 week, then canary-releasing endpoint by endpoint over 4 weeks.

REST to GraphQL migration: Implement GraphQL resolvers that call the existing REST endpoints internally, gradually replacing REST data fetching with direct database access while maintaining the REST surface via a thin GraphQL-to-REST adapter.

Monolith to microservices: Extract a user management module from a monolithic API into a standalone service, using the strangler fig pattern with API gateway routing to direct /users/* traffic to the new service while other endpoints remain on the monolith.

See ${CLAUDE_SKILL_DIR}/references/examples.md for additional examples.

Resources

  • Strangler Fig Application pattern: Martin Fowler
  • Feature flag services: LaunchDarkly, Unleash, Flagsmith
  • Traffic shadowing with Envoy proxy or Istio service mesh
  • Blue-green and canary deployment strategies

© jeremylongshore, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 3 other files (references) in skills/.curated/migrating-apis of jeremylongshore/tons-of-skills-marketplace.

  • SKILL.md
  • references/errors.md
  • references/examples.md
  • references/implementation.md

Open the folder on GitHubat commit cfae287

Compare with similar skills

Migrating APIs next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

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Migrating APIs this skilljeremylongshore/tons-of-skills-marketplace2.8k—~1.4kAutomated safety check: PassMIT
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Perf ComparisonClickHouse/ClickHouse50k—~3.9kAutomated safety check: NotesApache-2.0
Patch Release CheckClickHouse/ClickHouse50k—~4kAutomated safety check: NotesApache-2.0
Evolving The Data ModelTriliumNext/Trilium38k—~2.1kAutomated safety check: PassAGPL-3.0
Hybrid Cloud Outboxesgetsentry/sentry46k—~4.8kAutomated safety check: PassCustom licence

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Categories

Questions about Migrating APIs

What does Migrating APIs do?

Implement API migrations between versions, platforms, or frameworks with minimal downtime. Migrating APIs is an agent skill from jeremylongshore/tons-of-skills-marketplace. Implement API migrations between versions, platforms, or frameworks with minimal downtime.

When should I use Migrating APIs?

Migrating APIs fits situations like: upgrading APIs between versions; with phrases like migrate the API; upgrade API version; migrate to new API.

How do I install Migrating APIs in Claude Code?

Run `npx skills add jeremylongshore/tons-of-skills-marketplace --skill migrating-apis -a claude-code`. Or copy the skill folder (skills/.curated/migrating-apis in jeremylongshore/tons-of-skills-marketplace) into .claude/skills/migrating-apis in your project. Claude Code loads it when a task matches its description.

How do I install Migrating APIs in Codex?

Run `npx skills add jeremylongshore/tons-of-skills-marketplace --skill migrating-apis -a codex`. Or copy the skill folder (skills/.curated/migrating-apis in jeremylongshore/tons-of-skills-marketplace) into .agents/skills/migrating-apis in your project. Codex loads it when a task matches its description.

Can I use Migrating APIs in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add jeremylongshore/tons-of-skills-marketplace --skill migrating-apis -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/migrating-apis, .gemini/skills/migrating-apis, .github/skills/migrating-apis and .opencode/skills/migrating-apis in your project.

What does Migrating APIs need to run?

SKILL.md names no scripts, command-line tools or credentials: Migrating APIs is instructions for the agent only. Our summary lists: Python 3; Node.js. Its frontmatter pre-approves these tools: Read, Write, Edit, Grep, Glob, Bash(api:migrate-*). Compatibility (from SKILL.md): Designed for Claude Code.

Does Migrating APIs access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Migrating APIs safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Migrating APIs use?

Migrating APIs is published under the MIT licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Migrating APIs use?

About 1.4k tokens (SKILL.md is roughly 5.5k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 1.9k tokens, read only when the agent opens those files.

What are the alternatives to Migrating APIs?

Skills that share tags, products or a category with Migrating APIs: Keeper Stress Analysis (ClickHouse/ClickHouse, 50k stars), Perf Comparison (ClickHouse/ClickHouse, 50k stars), Patch Release Check (ClickHouse/ClickHouse, 50k stars) and Evolving The Data Model (TriliumNext/Trilium, 38k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Migrating APIs?

jeremylongshore (a GitHub user) maintains it in jeremylongshore/tons-of-skills-marketplace, which has 2,827 GitHub stars. The repository holds 3,342 skills in this directory. The repository was last updated on October 10, 2026.

Source: jeremylongshore/tons-of-skills-marketplace on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.