Derive API Client from Recorded Session

Records browser traffic once into a HAR file, reverse-engineers a site's internal API, and generates a standalone client or CLI that needs no browser afterwards.

Web & APIAdvanced★ 1,161⑂ 109AI score 9/10Last updated: Oct 3, 2026

What it does

Captures network traffic to a HAR file with agent-browser network har start/stop while you drive the site.
Filters out analytics, third-party domains, and static assets using jq, surfacing only the real first-party JSON endpoints.
Extracts request headers, POST bodies, and response payloads to infer types and auth material (authorization, cookie, x-csrf-token, custom x-* headers).
Generates a standalone client/CLI with one function per recorded flow (search(query), getItem(id)), loading credentials from a file or env var instead of hardcoding them.
Verifies every generated function against the live API, with a troubleshooting table for 401/403, per-session CSRF, signed/expiring params, and A/B-varying shapes.

Who it's for

Developers automating a site repeatedly that offers no public API.
Teams whose browser-driven scrapers are too slow and want direct HTTP calls instead.
Engineers documenting or exploring internal API endpoints of an existing app.

Example uses

"Reverse engineer this search site's API and build me a CLI" → record two searches and two detail pages, then emit a CLI with search and getItem.
"Derive a client for the list endpoint of this login-protected dashboard" → log in first, record the HAR, export cookies with cookies get --json, and load them at runtime.
"From yesterday's HAR, find the pagination params and write a bulk fetch script" → diff query strings for page/limit and generate a rate-limit-friendly collector.

· · · Install guide · · ·

Try it now, no install

Paste this into Claude to use the skill without installing anything.

Read the instructions in this file and follow them to help me:
https://raw.githubusercontent.com/fcakyon/claude-codex-settings/HEAD/plugins/agent-browser/skills/derive-client/SKILL.md

What I want: (describe your task here)

If Claude can't open the link, open it yourself and paste the contents instead.

↓ If it works for you, download the ZIP below and install it. Then it runs on its own — no pasting each time.

Install in the Claude app (no terminal)

Download the ZIP with the button below.
In Claude, open Settings → Capabilities and turn on 'Code execution and file creation'. (one time)
Go to Customize → Skills → + → 'Upload a skill' and upload the ZIP.

↓ Download ZIP

Install in Claude Code

Let Claude do it — paste this into Claude Code

Install the skill I found on Claude Skill Mart.
Copy the plugins/agent-browser/skills/derive-client folder from the GitHub repo fcakyon/claude-codex-settings into my ~/.claude/skills/derive-client/.
When it's done, tell me in one line what this skill can do.

Install with a command instead

git clone https://github.com/fcakyon/claude-codex-settings.git && mkdir -p ~/.claude/skills && cp -r claude-codex-settings/plugins/agent-browser/skills/derive-client ~/.claude/skills/

⚠ This is a third-party skill. Check the source repository before installing.

Open a terminal and move to your working directory.
Clone the repo: git clone https://github.com/fcakyon/claude-codex-settings.git
Create the skills directory: mkdir -p ~/.claude/skills
Copy the skill: cp -r claude-codex-settings/plugins/agent-browser/skills/derive-client ~/.claude/skills/
Install prerequisites: the agent-browser CLI (check with npx agent-browser --version) and jq (macOS: brew install jq).
Restart Claude Code, then ask something like "reverse engineer this site's API and build a client" to trigger the skill.
When finished, delete the HAR file and cookies.json — they contain live session credentials and must never be committed to version control.

View source on GitHub ↗License: Apache-2.0