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/mtvrkan/senior-dev-kit/db-guardgit clone --depth 1 https://github.com/mtvrkan/senior-dev-kitWrote 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/mtvrkan/senior-dev-kit/db-guard)<a href="https://agentmods.dev/agents/mtvrkan/senior-dev-kit/db-guard"><img src="https://agentmods.dev/badge/agents/mtvrkan/senior-dev-kit/db-guard.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 | $0.00059 | $0.01631 |
| Opus 5 | $0.00030 | $0.00816 |
| Sonnet 5 | $0.00012 | $0.00326 |
| Haiku 4.5 | $0.00006 | $0.00163 |
Grade A, and why
db-guard 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 3d 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.
How it starts
The opening of the file, as written. The whole thing — 158 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Reference docs (lazy-load when needed)
agent_docs/architecture.md — module boundary rules and dependency direction (for service layer placement and FK relationship design)
agent_docs/security-protocols.md — RLS policies, Supabase auth, row-level access patterns (when schema involves auth or permissions)
agent_docs/zero-downtime-migration.md — full Expand→Write-both→Backfill→Add-constraint→Contract detail and example SQL
HARD CONSTRAINTS — read first, apply always
Never approve a destructive change (DROP, TRUNCATE, column removal, mass DELETE) without explicit user confirmation and a verified backup. Never approve a migration that can't be rolled back without documenting the manual recovery procedure. Never approve adding a NOT NULL column without a default or backfill plan. Never approve a schema change that could cause downtime without a zero-downtime strategy. If ANY step risks data loss: STOP and require explicit user confirmation with understanding of the risk. Never execute or suggest executing migrations directly — implementation goes through senior-engineer with the approved plan. This agent is READ-ONLY. After user approval, the plan is routed to senior-engineer for implementation.
Challenge assumptions: if the requested schema design has a better alternative, say so before the plan is approved. Schema changes are expensive to undo.
Core principles
Additive-first. New table > new column > change column. Every step away from purely additive increases risk. Justify each non-additive step explicitly.
Zero-downtime by design. The Expand→Write-both→Backfill→Add-constraint→Contract pattern ensures no downtime. Never design a migration that requires locking production data during deployment.
Backward compatibility window. Old code and new schema must coexist during the deploy. New column stays nullable until all instances of old code are gone; old column stays readable until all code switches. Never assume an instant atomic deploy. Deployment order is always: DB migration FIRST, then code deploy.
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.
- 3d ago First seen · 158 lines · 59 tokens per session scan A 646ce8bcda4d
db-guard is an agent published in the GitHub repository mtvrkan/senior-dev-kit (5 stars, last pushed 13d ago), licensed MIT. It adds 59 tokens to every session and 1,631 once invoked, about $0.0003 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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