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 dkmqflx/nestjs-best-practices-plugin --skill nestjs-exception-filtersgit clone --depth 1 https://github.com/dkmqflx/nestjs-best-practices-pluginWrote 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/dkmqflx/nestjs-best-practices-plugin/nestjs-exception-filters)<a href="https://agentmods.dev/skills/dkmqflx/nestjs-best-practices-plugin/nestjs-exception-filters"><img src="https://agentmods.dev/badge/skills/dkmqflx/nestjs-best-practices-plugin/nestjs-exception-filters/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/dkmqflx/nestjs-best-practices-plugin/nestjs-exception-filters"><img src="https://agentmods.dev/badge/skills/dkmqflx/nestjs-best-practices-plugin/nestjs-exception-filters.svg" alt="Reviewed on agentmods" width="80" 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 | $0.00057 | $0.00595 |
| Opus 5 | $0.00028 | $0.00298 |
| Sonnet 5 | $0.00011 | $0.00119 |
| Haiku 4.5 | $0.00006 | $0.00060 |
Grade A, and why
nestjs-exception-filters 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 11d 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 — 40 lines — stays where its author put it; the contents beside it link to each section on GitHub.
NestJS Exception Handling & Filters
NestJS ships a built-in exceptions layer that catches unhandled exceptions and turns them into a sensible HTTP response. Lean on it: throw exceptions from your business logic and let filters shape the response. These rules cover throwing the right exception, modeling domain errors, and centralizing error formatting with global filters — for NestJS v10/v11.
When to Apply
- Throwing errors from controllers, services, guards, pipes, or interceptors.
- Designing custom/domain exception classes.
- Building a global exception filter (
APP_FILTER) or a catch-all filter. - Standardizing the JSON error body returned to clients.
- Reviewing code that manually builds error responses on
res.
Rules
| Rule | Impact | Summary |
|---|---|---|
| use-builtin-http-exceptions | HIGH | Throw BadRequestException/NotFoundException etc. instead of generic Error. |
| domain-exception-classes | MEDIUM | Model domain errors as custom classes extending HttpException. |
| global-exception-filter | HIGH | Register a global filter via APP_FILTER for consistent formatting. |
| catch-all-unknown-errors | HIGH | Use a @Catch() catch-all filter to map unknown errors to 500. |
| dont-leak-internal-details | CRITICAL | Never expose stack traces, SQL, or secrets; log them server-side only. |
| consistent-error-shape | MEDIUM | Return a uniform JSON error body across the API. |
| throw-dont-return-errors | HIGH | Let exceptions propagate to filters; don't hand-craft res in handlers. |
How to Use
- In handlers/services, throw built-in or domain exceptions — never construct the HTTP response by hand.
- Add one global catch-all filter (
APP_FILTER) that formats every error into your standard shape and maps unknown errors to 500. - In that filter, log full internals server-side and return only safe, client-facing fields.
- Skim the rule files above for the incorrect/correct examples before writing or reviewing error-handling code.
What ships with it
7 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.
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.
- 11d ago First seen · 40 lines · 57 tokens per session scan A b118281d4ad8
nestjs-exception-filters is a skill published in the GitHub repository dkmqflx/nestjs-best-practices-plugin (1 stars, last pushed 2mo ago), licensed MIT. It adds 57 tokens to every session and 595 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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