MCPInstall

ln-772-error-handler-setup

by levnikolaevichBackend & APIs

Configures global exception handling middleware. Use when adding centralized error handling to .NET or Python backends.

Installs
382
Last 24h
—
Trending rank
—
Security
Not audited

Install

Works with every agent the skills CLI supports.

npx skills add https://github.com/levnikolaevich/claude-code-skills --skill ln-772-error-handler-setup
  1. 01

    Install

    Run the command in your project. The CLI asks which agents to install for.

  2. 02

    Describe the task

    Ask your agent for something this skill covers. It loads ln-772-error-handler-setup automatically when relevant.

  3. 03

    Review the result

    The agent follows the SKILL.md steps, scripts and references bundled with the skill.

SKILL.md

The instructions your agent reads when the skill is triggered.

ln-772-error-handler-setup

Type: L3 Worker Category: 7XX Project Bootstrap

Configures global error handling for .NET and Python backend applications.

Overview

AspectDetails
InputContext Store from ln-770
OutputException handling middleware and custom exceptions
Stacks.NET (ASP.NET Core Middleware), Python (FastAPI exception handlers)

Phase 1: Receive Context

Accept Context Store from coordinator.

Required Context:

  • STACK: .NET or Python
  • FRAMEWORK: ASP.NET Core or FastAPI
  • PROJECT_ROOT: Project directory path
  • ENVIRONMENT: Development or Production

Idempotency Check:

  • .NET: Grep for GlobalExceptionMiddleware or UseExceptionHandler
  • Python: Grep for @app.exception_handler or exception_handlers.py
  • If found: Return { "status": "skipped" }

Phase 2: Research Error Handling Patterns

Use MCP tools to get up-to-date documentation.

For .NET:

MCP ref: "ASP.NET Core global exception handling middleware"
Context7: /dotnet/aspnetcore

For Python:

MCP ref: "FastAPI exception handlers custom exceptions"
Context7: /tiangolo/fastapi

Key Patterns to Research:

  1. Middleware pipeline positioning
  2. Exception type mapping to HTTP status codes
  3. ProblemDetails (RFC 7807) format
  4. Development vs Production error details
  5. Logging integration

Phase 3: Decision Points

Q1: Error Response Format

OptionDescription
ProblemDetails (RFC 7807) (Recommended)Standardized format, widely adopted
Custom FormatProject-specific requirements

Q2: Error Detail Level

EnvironmentStack TraceInner ExceptionsRequest Details
Development✓ Show✓ Show✓ Show
Production✗ Hide✗ Hide✗ Hide

Q3: Error Taxonomy

Define standard error codes:

CodeHTTP StatusDescription
VALIDATION_ERROR400Invalid input data
UNAUTHORIZED401Authentication required
FORBIDDEN403Insufficient permissions
NOT_FOUND404Resource not found
CONFLICT409Resource state conflict
INTERNAL_ERROR500Unexpected server error

Phase 4: Generate Configuration

.NET Output Files

FilePurpose
Middleware/GlobalExceptionMiddleware.csException handling middleware
Exceptions/AppException.csBase exception class
Exceptions/ValidationException.csValidation errors
Exceptions/NotFoundException.csNot found errors
Models/ErrorResponse.csError response model

Generation Process:

  1. Use MCP ref to get current ASP.NET Core exception handling patterns
  2. Generate GlobalExceptionMiddleware with:
    • Exception type to HTTP status mapping
    • Logging of exceptions
    • ProblemDetails response format
    • Environment-aware detail level
  3. Generate custom exception classes

Registration Code:

app.UseMiddleware<GlobalExceptionMiddleware>();

Python Output Files

FilePurpose
exceptions/app_exceptions.pyCustom exception classes
exceptions/handlers.pyFastAPI exception handlers
models/error_response.pyPydantic error models

Generation Process:

  1. Use MCP ref to get current FastAPI exception handling patterns
  2. Generate exception handlers with:
    • HTTPException handling
    • Custom AppException handling
    • Validation error handling
    • Request validation error handling
  3. Generate custom exception classes

Registration Code:

app.add_exception_handler(AppException, app_exception_handler)
app.add_exception_handler(RequestValidationError, validation_exception_handler)

Phase 5: Validate

Validation Steps:

  1. Syntax check:

    • .NET: dotnet build --no-restore
    • Python: python -m py_compile exceptions/handlers.py

  2. Test error handling:

    • Create test endpoint that throws exception
    • Verify error response format
    • Check that stack trace hidden in Production

Expected Error Response (ProblemDetails):

{
  "type": "https://tools.ietf.org/html/rfc7231#section-6.5.1",
  "title": "Validation Error",
  "status": 400,
  "detail": "Invalid input data",
  "instance": "/api/users",
  "errors": [
    { "field": "email", "message": "Invalid email format" }
  ],
  "traceId": "abc-123-def-456"
}

Return to Coordinator

{
  "status": "success",
  "files_created": [
    "Middleware/GlobalExceptionMiddleware.cs",
    "Exceptions/AppException.cs",
    "Models/ErrorResponse.cs"
  ],
  "packages_added": [],
  "registration_code": "app.UseMiddleware<GlobalExceptionMiddleware>();",
  "message": "Configured global exception handling"
}

Reference Links

Critical Rules

  • Use ProblemDetails (RFC 7807) by default — standardized error response format
  • Hide stack traces in Production — environment-aware detail level is mandatory
  • Use MCP ref for current patterns — do not hardcode middleware from memory
  • Idempotent — if GlobalExceptionMiddleware or exception_handlers.py exists, return status: "skipped"
  • Map all custom exceptions to HTTP status codes — no unhandled exception types reaching the client

Definition of Done

  • Context Store received (stack, framework, environment)
  • Error handling patterns researched via MCP tools
  • GlobalExceptionMiddleware generated (.NET) or exception handlers generated (Python)
  • Custom exception classes created (AppException, ValidationException, NotFoundException)
  • Error response model created (ProblemDetails format)
  • Syntax validated (dotnet build or py_compile)
  • Structured JSON response returned to ln-770 coordinator

Version: 2.0.0 Last Updated: 2026-01-10

FAQ

What does the ln-772-error-handler-setup skill do?

Configures global exception handling middleware. Use when adding centralized error handling to .NET or Python backends.

How do I install ln-772-error-handler-setup?

Run npx skills add https://github.com/levnikolaevich/claude-code-skills --skill ln-772-error-handler-setup in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/ln-772-error-handler-setup/ (personal) or .claude/skills/ln-772-error-handler-setup/ (project).

Which AI agents can use ln-772-error-handler-setup?

Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.

Is ln-772-error-handler-setup safe to install?

No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.

Who maintains ln-772-error-handler-setup?

It is published by levnikolaevich in levnikolaevich/claude-code-skills. It has 382 recorded installs.

More from levnikolaevich/claude-code-skills

View all →

ln-100-documents-pipeline

levnikolaevich/claude-code-skills

Creates complete project documentation system (project docs, reference, tasks, tests). Use when bootstrapping docs from scratch or regenerating all.

Docs & Writing479 installs

ln-620-codebase-auditor

levnikolaevich/claude-code-skills

Open the skill to read its SKILL.md instructions.

Code Quality & Workflow449 installs

ln-775-api-docs-generator

levnikolaevich/claude-code-skills

Configures Swagger/OpenAPI documentation for backend APIs. Use when adding interactive API docs to a project.

Backend & APIs432 installs

ln-624-code-quality-auditor

levnikolaevich/claude-code-skills

Checks cyclomatic complexity, nesting, long methods, god classes, O(n2), N+1 queries, constants management. Use when auditing code quality.

413 installs

ln-782-test-runner

levnikolaevich/claude-code-skills

Executes all test suites and reports results with coverage. Use when verifying that test infrastructure works after bootstrap.

Testing & QA412 installs

ln-634-test-coverage-auditor

levnikolaevich/claude-code-skills

Open the skill to read its SKILL.md instructions.

Testing & QA401 installs

Popular backend & apis skills

View category →

find-skills

vercel-labs/skills

Helps users discover and install agent skills when they ask questions like "how do I do X", "find a skill for X", "is there a skill that can...", or express interest in extending capabilities. This skill should be used when the user is looking for functionality that might exist as an installable skill.

OfficialBackend & APIs4.1M installs

entra-app-registration

microsoft/azure-skills

Guides Microsoft Entra ID app registration, OAuth 2.0 authentication, and MSAL integration. USE FOR: create app registration, register Azure AD app, configure OAuth, set up authentication, add API permissions, generate service principal, MSAL example, console app auth, Entra ID setup, Azure AD authentication. DO NOT USE FOR: Key Vault secrets (use azure-keyvault-expiration-audit), general Azure resource security guidance.

OfficialBackend & APIs566.7K installs

google-agents-cli-adk-code

google/agents-cli

This skill should be used when the user wants to "write agent code", "build an agent with ADK", "add a tool", "create a callback", "define an agent", "use state management" — in a project that needs ADK (Agent Development Kit) API patterns and code examples. It provides a quick reference for agent types, tool definitions, orchestration patterns, callbacks, state management, the graph Workflow API, and reference recipes to study. Do NOT use for scaffolding (use google-agents-cli-scaffold) or deployment (use google-agents-cli-deploy).

Backend & APIs514.8K installs

embedded-captions

heygen-com/hyperframes

Add captions or subtitles to an existing single-subject talking-head video without editing the footage. Use for plain verbatim captions, cinematic captions embedded behind the subject, VFX captions, “炸/特效/酷炫字幕,” or a named identity from the 35-style catalog. Route by visual identity, not by backend engine. The quiet anchor rail is the default; embed every word only when the user explicitly wants a fully cinematic treatment. The workflow runs locally end to end, including transcription and subject matting; split multi-shot footage before applying it.

Backend & APIs453.3K installs

entra-agent-id

microsoft/azure-skills

Provision Microsoft Entra Agent Identity Blueprints, BlueprintPrincipals, and per-instance Agent Identities via Microsoft Graph, and configure OAuth 2.0 token exchange (fmipath, OBO, cross-tenant) including the Microsoft Entra SDK for AgentID sidecar. USE FOR: Agent Identity Blueprint, BlueprintPrincipal, agent OAuth, fmipath token exchange, agent OBO, Workload Identity Federation for agents, polyglot agent auth, Microsoft.Identity.Web.AgentIdentities. DO NOT USE FOR: standard Entra app registration (use entra-app-registration), Microsoft Foundry agent authoring (use microsoft-foundry).

OfficialBackend & APIs336.6K installs

neon

neondatabase/agent-skills

Overview of Neon, a complete set of cloud backend primitives around Lakebase Postgres: Auth, Object Storage, Functions, the AI Gateway, and Realtime. Start here to choose Neon for undecided login, files, APIs, and LLM calls, set up the CLI or MCP server, and follow the branch-first workflow. Use when building an app or backend on Neon, or when "Neon" or "Lakebase Postgres" is mentioned. Child skill neon-postgres wins for an existing DATABASEURL, SQL, schema, inspect, or search. Child skill neon-auth wins for login, users, sessions, identity routing, and Managed Better Auth setup. Child skill neon-realtime wins for live queries in reactive apps and agents. Also use for object storage, S3, buckets, serverless functions, function triggers, cron, AI gateway, LLM calls, realtime, logs, Loki, Grafana, observability, postgres, database, backend, Claimable Neon, neon.new, or a no-signup database.

Backend & APIs237.1K installs