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 Cratis/AI --skill cratis-arc-ef-core-migrationgit clone --depth 1 https://github.com/Cratis/AIWrote 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/cratis/ai/cratis-arc-ef-core-migration)<a href="https://agentmods.dev/skills/cratis/ai/cratis-arc-ef-core-migration"><img src="https://agentmods.dev/badge/skills/cratis/ai/cratis-arc-ef-core-migration.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 5.1 | $0.00093 | $0.02556 |
| Opus 5 | $0.00046 | $0.01278 |
| Sonnet 5 | $0.00019 | $0.00511 |
| Haiku 4.5 | $0.00009 | $0.00256 |
Grade A, and why
cratis-arc-ef-core-migration 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 today.
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 — 232 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Change an EF Core schema in an Arc application
Arc adds three things to Entity Framework Core: DbContext base types that apply its conversions, cross-database column helpers for migrations, and a resolver that makes an EF Core read model injectable into a command by the command's key. Everything else is ordinary EF Core.
Verified product sources
| Package | Version | Purpose |
|---|---|---|
Cratis.Arc.EntityFrameworkCore |
22.10.4 |
BaseDbContext, ReadOnlyDbContext, WithEntityFrameworkCore, column helpers, EntityFrameworkReadModelForCommandResolver |
Cratis.Arc.Core |
22.10.4 |
Cratis.Arc.Queries.ModelBound.ReadModelAttribute, ICanResolveReadModelForCommand |
Microsoft.EntityFrameworkCore |
10.0.11 |
EF Core itself, including all migration tooling |
Reverify before claiming support for another version.
⚠️ Arc ships no migration tooling of its own. There is no design-time
DbContext factory, no migration runner, no table-name constant convention, and
nothing that reads or writes __EFMigrationsHistory anywhere in Arc. Migrations
are created and applied with the standard EF Core tooling. Guidance describing an
ApplyAllMigrations runner, a WellKnownTables class, or a mandatory
Database/Core/Infrastructure project split is describing one
application's local convention, not Arc.
Pick the DbContext base type
| Base | Use for |
|---|---|
ReadOnlyDbContext |
Read models and projections — the vast majority |
BaseDbContext |
A context that genuinely owns writable state |
Both take DbContextOptions through a primary constructor; neither has a
parameterless constructor, so the derived context must pass options through:
public class <Feature>DbContext(DbContextOptions<<Feature>DbContext> options)
: ReadOnlyDbContext(options)
{
public DbSet<<ReadModel>> <ReadModels> => Set<<ReadModel>>();
}
BaseDbContext.OnModelCreating applies Arc's JSON, ConceptAs<T> and Guid
conversions. Override OnModelCreating only after calling base — and do not
override OnConfiguring.
What ships with it
1 file 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.
- today First seen · 232 lines · 93 tokens per session scan A 6f10633b1aee
cratis-arc-ef-core-migration is a skill published in the GitHub repository Cratis/AI (2 stars, last pushed today), licensed MIT. It adds 93 tokens to every session and 2,556 once invoked, about $0.0005 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 2026-09-06.
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