Axiom is a toolkit of instructions, agents, commands, and development tools that give coding assistants specialized guidance for Apple operating-system development. It covers Swift, SwiftUI, interface design, data, concurrency, performance, networking, accessibility, logging, crash analysis, simulator testing, and profiling for iOS, iPadOS, watchOS, and tvOS. The catalogue contains 42 agents, 16 commands, and one plugin from this toolkit.
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 CharlesWiltgen/Axiom --skill axiom-datagit clone --depth 1 https://github.com/CharlesWiltgen/AxiomWrote 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/charleswiltgen/axiom/axiom-data)<a href="https://agentmods.dev/skills/charleswiltgen/axiom/axiom-data"><img src="https://agentmods.dev/badge/skills/charleswiltgen/axiom/axiom-data/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/charleswiltgen/axiom/axiom-data"><img src="https://agentmods.dev/badge/skills/charleswiltgen/axiom/axiom-data.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket pass
- Snyk pass
- NVIDIA SkillSpector warn
SkillSpector: 1 finding, up to high
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- high Privilege Escalation · line 124 Code accesses credential files (SSH keys, AWS credentials, etc.). This could indicate credential theft attempts.Fix: Remove references to credential paths. Use environment variables or secrets managers. For docs, use placeholder paths (e.g., /path/to/config). Never load .env or token files in production code paths.
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 | $0.00053 | $0.03415 |
| Opus 5.5 | $0.00021 | $0.01366 |
| Sonnet 5.5 | $0.00011 | $0.00683 |
| Haiku 4.5 | $0.00005 | $0.00342 |
Grade A, and why
axiom-data 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 9d 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 — 212 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Data & Persistence
You MUST use this skill for ANY data persistence, database, storage, CloudKit, or serialization work.
Can't launch Axiom agents? Where this router sends you to an agent, follow its procedure inline. Over MCP,
axiom_get_agentreturns it; elsewhere, read its file below, which needs only file search and read.Available here:
skills/codable-auditor.md,skills/core-data-auditor.md,skills/database-schema-auditor.md,skills/grdb-performance-auditor.md,skills/icloud-auditor.md,skills/storage-auditor.md,skills/swiftdata-auditor.md.For any other agent, over MCP
axiom_get_agentreturns it too; run its xclog, xcsym and xcprof steps with theaxiom_xclog_*,axiom_xcsym_*andaxiom_xcprof_*tools. Elsewhere, search Axiom's skills forskills/<agent>.md; if there is none, do that work yourself with this suite's skills, using any Axiom tool on yourPATH.
When to Use
Use this skill when working with:
- Databases (SwiftData, Core Data, GRDB, SQLiteData)
- Schema migrations
- CloudKit sync
- File storage (iCloud Drive, local storage)
- Data serialization (Codable, JSON)
- Storage strategy decisions
- Keychain / secure credential storage
- Encryption, signing, key management (CryptoKit)
Quick Reference
| Symptom / Task | Reference |
|---|---|
SwiftData @Model, @Query, ModelContext, sectioned queries / ResultsObserver / @Attribute(.codable) / dynamic compound predicates (OS27) |
See skills/swiftdata.md |
| SwiftData schema migration, VersionedSchema | See skills/swiftdata-migration.md |
| SwiftData migration crashes, data loss | See skills/swiftdata-migration-diag.md |
| Migrating from Realm to SwiftData | See skills/realm-migration-ref.md |
| SwiftData vs SQLiteData decision | See skills/sqlitedata-migration.md |
| GRDB queries, upsert, ValueObservation, DatabaseMigrator, encryption | See skills/grdb.md |
| GRDB performance, indexes, EXPLAIN QUERY PLAN, cursors, observation not firing | See skills/grdb-performance.md |
| Full-text search (FTS5) in GRDB or SQLiteData | See skills/sqlite-fts-ref.md |
| Storing or querying JSON inside a SQLite column (JSON1, JSONB) | See skills/sql-json-ref.md |
| GRDB shared across app + widget/extension (App Group) | See skills/grdb-app-groups.md |
| SQLiteData @Table, CRUD, SyncEngine | See skills/sqlitedata.md |
| SQLiteData advanced patterns, CTEs, views | See skills/sqlitedata-ref.md |
@Shared / @SharedReader, appStorage or fileStorage persistence, custom SharedKey, isLoading / loadError on @FetchAll |
See skills/swift-sharing.md |
| Core Data stack, relationships, concurrency | See skills/core-data.md |
| Core Data migration crashes, thread errors | See skills/core-data-diag.md |
| ANY schema migration safety | See skills/database-migration.md |
| Codable, JSON encoding/decoding | See skills/codable.md |
| Cloud sync architecture, offline-first | See skills/cloud-sync.md |
| CloudKit, CKSyncEngine, CKRecord | See skills/cloudkit-ref.md |
| iCloud Drive, ubiquitous containers | See skills/icloud-drive-ref.md |
| Cloud sync errors, conflict resolution | See skills/cloud-sync-diag.md |
| Storage strategy, where to store data | See skills/storage.md |
| Storage issues, files disappeared | See skills/storage-diag.md |
| Storage management, disk pressure | See skills/storage-management-ref.md |
| Keychain / secure credential storage | See axiom-security (skills/keychain.md) |
| Keychain errors (errSecDuplicateItem) | See axiom-security (skills/keychain-diag.md) |
| Keychain API reference | See axiom-security (skills/keychain-ref.md) |
| Encryption / signing / key management | See axiom-security (skills/cryptokit.md) |
| CryptoKit API reference | See axiom-security (skills/cryptokit-ref.md) |
| File protection, NSFileProtection | See axiom-security (skills/file-protection-ref.md) |
| tvOS data persistence (no guaranteed-persistent local storage) | See axiom-swift (skills/tvos.md) |
| tvOS + CloudKit SyncEngine | See skills/sqlitedata.md |
What ships with it
31 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.
- skills/cloud-sync-diag.md 22 KB
- skills/cloud-sync.md 15 KB
- skills/cloudkit-ref.md 22 KB
- skills/codable-auditor.md 20 KB
- skills/codable.md 24 KB
- skills/core-data-auditor.md 14 KB
- skills/core-data-diag.md 38 KB
- skills/core-data.md 13 KB
- skills/database-migration.md 20 KB
- skills/database-schema-auditor.md 17 KB
- skills/grdb-app-groups.md 25 KB
- skills/grdb-performance-auditor.md 26 KB
- skills/grdb-performance.md 30 KB
- skills/grdb.md 26 KB
- skills/icloud-auditor.md 18 KB
- skills/icloud-drive-ref.md 13 KB
- skills/realm-migration-ref.md 24 KB
- skills/sql-json-ref.md 20 KB
- skills/sqlite-fts-ref.md 34 KB
- skills/sqlitedata-migration.md 9.7 KB
- skills/sqlitedata-ref.md 35 KB
- skills/sqlitedata.md 32 KB
- skills/storage-auditor.md 18 KB
- skills/storage-diag.md 15 KB
- skills/storage-management-ref.md 20 KB
- skills/storage.md 18 KB
- skills/swift-sharing.md 13 KB
- skills/swiftdata-auditor.md 16 KB
- skills/swiftdata-migration-diag.md 19 KB
- skills/swiftdata-migration.md 29 KB
- skills/swiftdata.md 45 KB
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.
- 9d ago Changed 3cd6a67a0a16
- 1mo ago Changed e061421fb208
- 1mo ago Changed · +4 tokens per session 63f1b01d90d0
- 1mo ago Changed · +9 lines ccd7417451c8
- 1mo ago First seen · 203 lines · 49 tokens per session scan A 3f5bcf3f4aa7
axiom-data is a skill published in the GitHub repository CharlesWiltgen/Axiom (1,228 stars, last pushed 5d ago), licensed MIT. It adds 53 tokens to every session and 3,415 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 2026-09-06.
Other skills, from other repositories
alloydb-basics
Manages clusters, instances, and backups for AlloyDB for PostgreSQL, and integrates with AlloyDB Model Context Protocol (MCP) tools for automated database operations. Use when creating, configuring, or administering AlloyDB databases. Do NOT use for general PostgreSQL instances (e.g. Cloud SQL) or other GCP databases.
postgresql-table-design
Use this skill when designing or reviewing a PostgreSQL-specific schema. Covers best-practices, data types, indexing, constraints, performance patterns, and advanced features.
db-repair
Auto-fix gbrain's Postgres access so the brain stays available. When any gbrain command or MCP tool result carries a GBRAINDBACCESS marker (or an operator reports the brain database is down), run the hardcoded gbrain db-repair ladder: diagnose, apply the safe tier, verify. The action is ALWAYS the hardcoded command …
volcengine-rds-postgresql
A tool for operating PostgreSQL databases hosted by Volcano Engine's managed database service. PostgreSQL is a relational database used to store structured application data.
analyzing-insights-across-teams
Analyze PostHog insights, dashboards, or teams beyond the current project by querying the prod Postgres replicas synced into the dogfood data warehouse (US project 2, "PostHog App + Website"). Use when asked to analyze insights across all teams or projects, another team's insights, or fleet-wide insight/dashboard…
dsql
Build with Aurora DSQL — manage schemas, execute queries, handle migrations, diagnose query plans, diagnose cluster performance, load data, and develop applications with a serverless, distributed SQL database. Covers IAM auth, multi-tenant patterns, MySQL-to-DSQL and PostgreSQL-to-DSQL schema conversion, foreign key…