Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add cyborg-garden/hermes-agent-mt --skill har-derived-api-clientgit clone --depth 1 https://github.com/cyborg-garden/hermes-agent-mtWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/cyborg-garden/hermes-agent-mt/har-derived-api-client)<a href="https://agentmods.dev/skills/cyborg-garden/hermes-agent-mt/har-derived-api-client"><img src="https://agentmods.dev/badge/skills/cyborg-garden/hermes-agent-mt/har-derived-api-client/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/cyborg-garden/hermes-agent-mt/har-derived-api-client"><img src="https://agentmods.dev/badge/skills/cyborg-garden/hermes-agent-mt/har-derived-api-client.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00019 | $0.02651 |
| Opus 5.5 | $0.00008 | $0.01060 |
| Sonnet 5.5 | $0.00004 | $0.00530 |
| Haiku 4.5 | $0.00002 | $0.00265 |
Grade A, and why
har-derived-api-client scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 4d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
is pure stdlib, replay needs only `requests`/`httpx` (or `curl`). This is a copy
98% identical to har-derived-api-client — 15 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 164 lines — stays where its author put it; the contents beside it link to each section on GitHub.
HAR-Derived API Client
Drive a website once with a real browser while recording its network traffic to a HAR file, then distill that HAR into the site's private JSON API so you can call it directly with plain HTTP — far cheaper and faster than browser-controlling the page on every request. Credit: trick by Jared Longster, popularized by Dax (thdxr). This captures and replays; it does NOT bypass auth, solve CAPTCHAs, or defeat bot-detection — if the site needs a logged-in session, you carry its headers/cookies forward, you don't forge them.
The scripts are stdlib-plus-Playwright: capture needs Playwright, derivation
is pure stdlib, replay needs only requests/httpx (or curl).
Covers every Hermes browser pathway: the default local browser_navigate
backend, plus the cloud/remote backends (Browserbase, Browser-Use, Firecrawl)
and any /browser connect CDP endpoint. There are two capture scripts — one
for a browser you launch, one for a browser you attach to over CDP — because
HAR recording works differently in each case (see How to Run).
When to Use
- "Build a CLI/client for " — derive its API instead of scripting clicks.
- "This site has no public API but the page clearly fetches JSON."
- You're about to loop
browser_navigatefor the same query repeatedly — stop and derive the endpoint once. - Reverse-engineering an autocomplete, search, feed, or checkout XHR.
- You captured a session on a cloud backend (Browserbase / Browser-Use / Firecrawl) or via
/browser connectand want the API without re-renting the browser.
Prerequisites
- Playwright + a browser binary (capture step only):
pip install playwrightthenplaywright install chromium --no-shell- (If a system Playwright already has browsers under
~/.cache/ms-playwright, reuse it.)
requestsorhttpxfor the replay step (stdliburllibalso works).- No API keys. Any keys/tokens the client needs are the ones the HAR captured.
- For the CDP path (
har_capture_cdp.py): a reachable CDP endpoint. On Hermes, run/browser connectto print the active endpoint, or readBROWSER_CDP_URL/browser.cdp_urlin config. Cloud backends expose it ascdpUrl/connectUrl.
What ships with it
3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 4d ago First seen · 164 lines · 19 tokens per session scan A 6645d1a0403f
har-derived-api-client is a skill published in the GitHub repository cyborg-garden/hermes-agent-mt (14 stars, last pushed yesterday), licensed MIT. It adds 19 tokens to every session and 2,651 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 1 finding (makes network calls). It is 98% identical to har-derived-api-client, differing in 15 lines, and is treated as a copy.
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