Borrowing it
Nothing to install: this file belongs to thunder-id/thunderid. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/thunder-id/thunderid/main/.agent/skills/backend/SKILL.mdgit clone --depth 1 https://github.com/thunder-id/thunderidWrote 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/thunder-id/thunderid/backend)<a href="https://agentmods.dev/skills/thunder-id/thunderid/backend"><img src="https://agentmods.dev/badge/skills/thunder-id/thunderid/backend/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/thunder-id/thunderid/backend"><img src="https://agentmods.dev/badge/skills/thunder-id/thunderid/backend.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 | $0.00072 | $0.00312 |
| Opus 5.5 | $0.00029 | $0.00125 |
| Sonnet 5.5 | $0.00014 | $0.00062 |
| Haiku 4.5 | $0.00007 | $0.00031 |
Grade A, and why
backend scanned grade A with 0 findings 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 6d 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.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
What it actually says
Backend Conventions
Read with backend/AGENTS.md. Schema and query rules are in the db skill, test rules in the backend-tests skill.
Read every reference file whose row matches the change:
| The change... | Read |
|---|---|
| Adds a file or package, or moves code between files | layout.md |
Adds an exported name, wires a dependency through init.go, or starts a background worker |
visibility.md |
| Adds or changes an error | errors.md |
| Adds or changes a log line | logging.md |
| Adds any new code: scope, constants, types, helpers, names, comments, user-facing text | idiom.md |
| Adds a management resource, or a store mode, export, or import to one | resource.md |
| Adds or changes a server configuration key | config.md |
Before adding anything, open the closest existing package and match its shape. When a rule here and an older package disagree, follow the rule.
What ships with it
7 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.
- 6d ago First seen · 24 lines · 72 tokens per session scan A 689fdae2c267
backend is a skill published in the GitHub repository thunder-id/thunderid (594 stars, last pushed yesterday), licensed Apache-2.0. It adds 72 tokens to every session and 312 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-10-21.
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