# APITC — API Troubleshooting Center

APITC is an independent, local-first reference for API failures and integration behavior. Its browser tools process pasted evidence in the active tab.

## Sections
- https://apitc.com/api-errors — API error index: status codes and provider failures
- https://apitc.com/headers — HTTP and API header reference
- https://apitc.com/protocols — API reliability protocols: retries, idempotency, pagination
- https://apitc.com/errors — LLM tool schema errors: OpenAI, Anthropic, Gemini, MCP
- https://apitc.com/convert — Tool schema converters
- https://apitc.com/compare — Provider schema comparisons
- https://apitc.com/guides — Agent tool contract guides
- https://apitc.com/tools — Workbench index
- https://apitc.com/atlas — API Protocol Atlas (6 provider profiles)
- https://apitc.com/search — Site search

## Workbenches
- https://apitc.com/tools/incident-decoder — API response and error decoder
- https://apitc.com/tools/cors-preflight-lab — CORS preflight policy simulator
- https://apitc.com/tools/rate-limit-header-analyzer — RateLimit, X-RateLimit, Retry-After, and bucket header analyzer
- https://apitc.com/tools/retry-backoff-planner — Exponential backoff, jitter, and idempotency planner
- https://apitc.com/tools/openapi-impact-diff — OpenAPI JSON breaking-change checker
- https://apitc.com/tools/tool-schema-compiler — OpenAI, Anthropic, Gemini, and MCP tool schema compiler

## API failure index
- https://apitc.com/api-errors/api-429-too-many-requests-retry-after
- https://apitc.com/api-errors/api-401-unauthorized-vs-403-forbidden
- https://apitc.com/api-errors/api-400-bad-request-json-body
- https://apitc.com/api-errors/api-422-unprocessable-content-validation
- https://apitc.com/api-errors/api-409-conflict-idempotency
- https://apitc.com/api-errors/api-502-503-504-upstream-errors
- https://apitc.com/api-errors/api-cors-preflight-failed

## Provider-specific troubleshooting
- https://apitc.com/api-errors/openai-429-insufficient-quota-vs-rate-limit
- https://apitc.com/api-errors/anthropic-529-overloaded-error
- https://apitc.com/api-errors/gemini-api-key-not-valid
- https://apitc.com/api-errors/stripe-webhook-signature-verification-failed
- https://apitc.com/api-errors/github-rest-api-bad-credentials-401
- https://apitc.com/api-errors/twilio-error-20003-authentication

## Protocol data and references
- https://apitc.com/atlas — provider protocol comparison dataset
- https://apitc.com/headers/retry-after-header-seconds-vs-date
- https://apitc.com/headers/ratelimit-limit-remaining-reset
- https://apitc.com/headers/idempotency-key-header
- https://apitc.com/headers/www-authenticate-header
- https://apitc.com/headers/access-control-allow-origin-header
- https://apitc.com/headers/etag-if-none-match-api-cache
- https://apitc.com/protocols/api-retry-exponential-backoff-jitter
- https://apitc.com/protocols/api-idempotency-post-requests
- https://apitc.com/protocols/api-pagination-offset-vs-cursor
- https://apitc.com/protocols/api-error-response-format-rfc-9457