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 skills/catwillgh/mainframe/mainframe-typescript-backendnpx skills add CATWILLgh/MAINFRAME --skill mainframe-typescript-backendgit clone --depth 1 https://github.com/CATWILLgh/MAINFRAMEWhat 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 | $0.00100 | $0.00891 |
| Opus 5 | $0.00050 | $0.00445 |
| Sonnet 5 | $0.00020 | $0.00178 |
| Haiku 4.5 | $0.00010 | $0.00089 |
Grade A, and why
mainframe-typescript-backend 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 — 72 lines — stays where its author put it; the contents beside it link to each section on GitHub.
TypeScript backend engineering
Discover the active package and installed stack before choosing an approach. Never infer the framework, router, runtime, ORM, or test path from a repository name or dependency list alone.
Work sequence
- Run
node scripts/recon.js <package-root>from this skill, or follow recon.md manually. - Trace the affected behavior through its entrypoint, business rules, data or external boundary, callers, and observable output.
- Read only the references matching the active path and changed risk.
- Verify installed versions and version-sensitive behavior through current primary documentation or Context7.
- Use the project's native commands and the smallest faithful red-to-green test. Read testing.md when selecting a test level, changing existing tests, or separating local and CI checks.
Several frameworks, ORMs, validators, auth libraries, or test runners are observations, not automatic blockers. Resolve the active owner from imports, configuration, runtime wiring, and affected files. Escalate only an unresolved choice that changes product behavior, infrastructure, permissions, or the assigned result.
Complete the assigned behavior. Do not substitute TODOs, placeholders, skipped or weakened tests, suppressions, or deferred in-scope work for implementation.
Preserve or introduce deliberately
- In an established system, preserve its supported runtime, framework, module format, ORM, auth, validation, contracts, and conventions. Make the smallest coherent change; do not add a competing library or incidental migration.
- In a new isolated component, prefer a supported Node.js LTS line, strict TypeScript, explicit boundaries, maintained libraries, focused tests, and PostgreSQL when relational semantics are required. Select libraries from the real requirements rather than a universal preferred stack.
Reference routing
| Changed concern | Read |
|---|---|
| Node.js, TypeScript, modules, packages, runtimes | runtime.md |
| NestJS, Express, Fastify | frameworks.md |
| Next.js server code | nextjs-server.md |
| HTTP, validation, OpenAPI, webhooks | contracts.md |
| Sessions, JWT, OAuth/OIDC, service auth | auth.md |
| Prisma, TypeORM, Drizzle, raw PostgreSQL | data-access.md |
| Schema and data rollout | migrations.md |
| Queues, schedulers, WebSockets | background-and-realtime.md |
| Files, caches, outbound calls, resilience | files-and-resilience.md |
| Logging, health, shutdown, telemetry | observability-and-lifecycle.md |
| Test scope, cost, and local/CI split | testing.md |
What ships with it
14 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.
- agents/openai.yaml 226 B
- references/auth.md 1.2 KB
- references/background-and-realtime.md 1.1 KB
- references/contracts.md 1.2 KB
- references/data-access.md 1.1 KB
- references/files-and-resilience.md 1.3 KB
- references/frameworks.md 1.1 KB
- references/migrations.md 1.0 KB
- references/nextjs-server.md 1.4 KB
- references/observability-and-lifecycle.md 1.1 KB
- references/recon.md 1.1 KB
- references/runtime.md 1.2 KB
- references/testing.md 2.3 KB
- scripts/recon.js 4.4 KB runs code
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 · 72 lines · 100 tokens per session scan A 5f75f6816592
mainframe-typescript-backend is a skill published in the GitHub repository CATWILLgh/MAINFRAME (2 stars, last pushed 12d ago), licensed MIT. It adds 100 tokens to every session and 891 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 2026-08-31.
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