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 rules/goranerhartic/cursor-development-rules/data-fetchinggit clone --depth 1 https://github.com/GoranErhartic/cursor-development-rulesWrote 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/rules/goranerhartic/cursor-development-rules/data-fetching)<a href="https://agentmods.dev/rules/goranerhartic/cursor-development-rules/data-fetching"><img src="https://agentmods.dev/badge/rules/goranerhartic/cursor-development-rules/data-fetching.svg" alt="Measured on agentmods" 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 | $0.00016 | $0.00471 |
| Opus 5 | $0.00008 | $0.00235 |
| Sonnet 5 | $0.00003 | $0.00094 |
| Haiku 4.5 | $0.00002 | $0.00047 |
Grade A, and why
data-fetching 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 today.
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.
What it actually says
Data Fetching with TanStack Query
Setup
- Wrap app with
QueryClientProvider; createQueryClientwithdefaultOptions(staleTime, gcTime, retry, refetchOnWindowFocus as needed)
Queries
- useQuery:
queryKey: ['resource', id](or['users', 'search', params]);queryFn: async () => fetch/return;enabled: booleanfor conditional fetch - States:
isLoading,isError,error,data,isFetching,refetch - Query key: Include all dependencies (filters, pagination) so cache is correct; use consistent key shape across app
Mutations
- useMutation:
mutationFn: async (variables) => api.post(...);onSuccess,onError,onSettled;mutateormutateAsync - Invalidation:
queryClient.invalidateQueries({ queryKey: ['users'] })after create/update/delete - Optimistic updates:
onMutate→ set cache withqueryClient.setQueryData;onError→ rollback withqueryClient.setQueryData(previous);onSettled→ invalidate
Conventions
- Server state in TanStack Query; local/UI state in useState/Zustand
- Loading: use
isLoadingfor initial,isFetchingfor background refetch - Error: render error UI from
error; use error boundary for unexpected - Prefetch:
queryClient.prefetchQuery({ queryKey, queryFn })on hover or route loader
Best Practices
- Sensible staleTime/gcTime; retry with backoff; keys include all variables; invalidate after mutations; optimistic updates where UX benefits; prefetch on intent
Anti-Patterns
- Fetch in useEffect for server data (use loader or useQuery); duplicate query keys; not invalidating after mutation; ignoring loading/error states; storing server state in Zustand
See also: routing.mdc, state-management.mdc, error-handling.mdc
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.
- today First seen · 39 lines · 16 tokens per session scan A 570e2ca290cf
data-fetching is a cursor rule published in the GitHub repository GoranErhartic/cursor-development-rules (19 stars, last pushed 6mo ago), licensed MIT. It adds 16 tokens to every session and 471 once invoked, about $0.0001 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 2026-09-03.
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