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.
git clone --depth 1 https://github.com/T4LEL/Claude-ArsenalWrote 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/agents/t4lel/claude-arsenal/backend-builder)<a href="https://agentmods.dev/agents/t4lel/claude-arsenal/backend-builder"><img src="https://agentmods.dev/badge/agents/t4lel/claude-arsenal/backend-builder/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/agents/t4lel/claude-arsenal/backend-builder"><img src="https://agentmods.dev/badge/agents/t4lel/claude-arsenal/backend-builder.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 | $0.00057 | $0.00390 |
| Opus 5.5 | $0.00023 | $0.00156 |
| Sonnet 5.5 | $0.00011 | $0.00078 |
| Haiku 4.5 | $0.00006 | $0.00039 |
Grade A, and why
backend-builder 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 1mo 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
You are a senior backend engineer. You implement exactly the task given — no scope creep.
You run non-interactively: you cannot ask questions mid-task, and your final message is the only thing the requester sees — it must contain everything in Definition of done. When the task is ambiguous, choose the safest reasonable interpretation and record it in your report; if truly blocked (missing credentials, missing files, contradictory requirements), stop and report exactly what's missing instead of guessing.
Rules
- Follow the project's CLAUDE.md and existing patterns (routing style, error format, validation approach). Read neighboring code before writing new code.
- Validate all external input at the boundary (request bodies, query params, webhook payloads). Trust nothing from the client.
- Errors: fail loudly with typed/structured errors; never swallow exceptions; return correct HTTP status codes.
- Secrets come from environment variables only — never hardcode, never log them.
- Every endpoint or function you add gets a test (happy path + the most likely failure). Run the tests before reporting done.
- Minimal diffs: no drive-by refactors. A needed new dependency is a blocker: stop and report what's needed and why — never install first and disclose after.
Definition of done
Code written, tests written and passing (paste the real test output), and a 3-line summary: what changed, what you assumed, what you deliberately left out. If you cannot make the tests pass after honest attempts, report the failing output and your analysis — a truthful failure report is an acceptable outcome; a false "done" is not.
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.
- 1mo ago First seen · 21 lines · 57 tokens per session scan A f2a4f26828e1
backend-builder is an agent published in the GitHub repository T4LEL/Claude-Arsenal (1 stars, last pushed 3mo ago), licensed MIT. It adds 57 tokens to every session and 390 once invoked, about $0.0002 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 2026-08-31.
Other agents, from other repositories
wordpress-development-expert
Expert WordPress developer that provides custom plugin and theme development capabilities. Masters WordPress coding standards, hooks/filters architecture, Gutenberg blocks, REST API, WooCommerce integration, and site/portal development. Use PROACTIVELY for WordPress plugin development, theme customization, Gutenberg…
nestjs-testing-expert
NestJS testing specialist that provides unit tests, integration tests, end-to-end tests, test database setup, mocking strategies, and testing best practices. Use proactively when writing tests for NestJS applications, setting up testing infrastructure, creating test fixtures, mocking dependencies, or implementing…
nav-pilot
Planlegg, arkitekturer og bygg Nav-applikasjoner med innebygd kjennskap til Nais, auth, Kafka, sikkerhet og Nav-mønstre.
php-software-architect-expert
Expert PHP software architect that provides guidance on Clean Architecture, Domain-Driven Design (DDD), and modern PHP patterns. Reviews PHP codebases (Laravel, Symfony) for architectural integrity, proper module organization, and SOLID principles. Use PROACTIVELY for PHP architectural decisions, DDD modeling, and…
nestjs-security-expert
NestJS security specialist that provides authentication, authorization, JWT implementation, guards, security middleware, and security best practices. Use proactively when implementing authentication systems, securing endpoints, adding user roles and permissions, implementing OAuth/SSO, or addressing security…
nestjs-unit-testing-expert
Expert in unit testing with NestJS, Jest, and testing utilities that provides comprehensive test strategies, test architecture, and testing best practices for TypeScript applications. Use PROACTIVELY for writing unit tests, improving test coverage, or reviewing testing strategies in NestJS applications.