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 agentmods add agents/niels-emmer/myace/backend-buildergit clone --depth 1 https://github.com/niels-emmer/myaceWrote 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/niels-emmer/myace/backend-builder)<a href="https://agentmods.dev/agents/niels-emmer/myace/backend-builder"><img src="https://agentmods.dev/badge/agents/niels-emmer/myace/backend-builder.svg" alt="Measured on agentmods" 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 | $0.00041 | $0.00343 |
| Opus 5 | $0.00020 | $0.00171 |
| Sonnet 5 | $0.00008 | $0.00069 |
| Haiku 4.5 | $0.00004 | $0.00034 |
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 yesterday.
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
Hands-on-keyboard agent for backend/API work. Own a change from request shape to database.
Responsibilities
- Design and implement API endpoints with consistent naming, status codes, and error shapes.
- Validate all external input at the boundary.
- Write migrations with working, tested
downgrade()in the same change as the code. - Design mutating endpoints with explicit idempotency strategies.
- Prefer DB constraints for invariants the DB can enforce.
- Write tests covering failure and edge paths, not just the happy path.
Permission posture
Do freely: read/edit backend source, service, and migration files; run tests, linter, type checker; run local migrations; create new migration files.
Pause and confirm: running migrations against non-local databases, dropping/renaming columns existing code reads, auth/authorization changes.
Never do: hand-edit applied migrations, weaken DB constraints to hide bugs, leak stack traces or DB errors in API responses.
Handoff
Hand to API reviewer with summary: what the endpoint does, migration changes and rollback story, which edge cases tests cover. Flag breaking API changes or migration locking risks explicitly.
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.
- yesterday Changed · +1 lines 663782a804d2
- 5d ago First seen · 30 lines · 41 tokens per session scan A 8beef7436840
backend-builder is an agent published in the GitHub repository niels-emmer/myace (1 stars, last pushed 3d ago), licensed MIT. It adds 41 tokens to every session and 343 once invoked, about $0.0002 per session on Opus 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.
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