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 filestack/filestack-claude-plugin --skill filestack-error-diagnosisgit clone --depth 1 https://github.com/filestack/filestack-claude-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/filestack/filestack-claude-plugin/filestack-error-diagnosis)<a href="https://agentmods.dev/skills/filestack/filestack-claude-plugin/filestack-error-diagnosis"><img src="https://agentmods.dev/badge/skills/filestack/filestack-claude-plugin/filestack-error-diagnosis/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/filestack/filestack-claude-plugin/filestack-error-diagnosis"><img src="https://agentmods.dev/badge/skills/filestack/filestack-claude-plugin/filestack-error-diagnosis.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 | $0.00099 | $0.01025 |
| Opus 5 | $0.00049 | $0.00513 |
| Sonnet 5 | $0.00020 | $0.00205 |
| Haiku 4.5 | $0.00010 | $0.00103 |
Grade A, and why
filestack-error-diagnosis 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 — 82 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Filestack Error Diagnosis
Error Response Shape
Filestack APIs return errors in two formats:
v1 API format (api.filestackapi.com):
{ "result": "error", "error": { "code": 403, "msg": "Policy required" } }
Processing/CDN format (process.filestackapi.com, cdn.filestackcontent.com):
{ "error": "Unsupported conversion" }
(v1 API includes a top-level result field; the processing/CDN edge does not — just error with a string or object.)
HTTP Error Code Reference
| Code | Meaning | Likely Cause | Fix |
|---|---|---|---|
| 401 | Unauthorized | Invalid or missing API key | Check FILESTACK_API_KEY is correct and hasn't been rotated |
| 403 | Forbidden | Security policy violation, or CORS origin not whitelisted | See policy errors below |
| 404 | Not Found | Handle doesn't exist, has been deleted, or has expired | Verify handle is correct; check app's handle expiry setting |
| 429 | Rate Limited | Too many requests | Read Filestack rate-limit headers (below); implement exponential backoff |
| 500/502/503 | Server Error | Transient Filestack service issue | Retry with backoff; check status.filestack.com |
Security Policy Errors (403)
403s from security-enabled apps are usually one of:
-
Expired policy —
expiryunix timestamp is in the pastimport time policy = { "expiry": int(time.time()) + 3600, "call": ["read"] } # 1 hour from now -
Wrong signature — HMAC computed with wrong secret, or policy was modified after signing
- Re-generate both policy and signature together — never modify the policy JSON after signing
-
Insufficient
callscope — policy doesn't include the operation being performedreadfor CDN delivery,storefor upload,convertfor transformations,removefor delete
-
Wrong CORS origin — browser request blocked
- Filestack dashboard → your app → Security → add your domain
Transformation Errors
| Error | Cause | Fix |
|---|---|---|
| "Unsupported input format" | Input file format not supported by the transform | Check Filestack docs for supported input formats per transform |
| "Output size limit exceeded" | Result would be larger than the app's output limit | Reduce target dimensions or use progressive encoding |
| "Processing timeout" | Transform took too long (usually video) | Use async transforms with a callback URL for video |
| "Invalid parameter" | Wrong parameter name or value type | Check CDN URL syntax: param:value (colon, not =) |
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 · 82 lines · 99 tokens per session scan A 977ce620be64
filestack-error-diagnosis is a skill published in the GitHub repository filestack/filestack-claude-plugin (3 stars, last pushed today), licensed MIT. It adds 99 tokens to every session and 1,025 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.
Other skills, from other repositories
printing-press-amend
Amend a published CLI from one of two input sources: (1) dogfood mode mines the active Claude Code session transcript for friction (missing flags, hand- rolled API payloads, silent-null returns); (2) direct-input mode accepts user-supplied asks (rename a command, add commands or feeds, fix a named bug, optionally…
convex-performance-audit
Audits Convex performance for reads, subscriptions, write contention, and function limits. Use for slow features, insights findings, OCC conflicts, or read amplification.
convex-insights
Query a running Convex app's logs + health in natural language (official MCP): failures, slow/expensive functions, deploy causality — scoped, evidence-backed, with a dashboard deep link.
ssl-proxy-troubleshoot
Systematic workflow for troubleshooting SSL/proxy connectivity issues with government websites.
diagnose-backend-bug
Diagnose a bounded backend or multi-service failure from GitHub Issues, Jira, Aone, user-provided exports, logs, traces, responses, stack traces, or job records. Use when a service, API, RPC, worker, queue, CLI, or scheduled job bug needs correlation through the project's existing observability route before repair; do…
axiom-networking
Use when implementing or debugging ANY network connection, API call, or socket. Covers URLSession, Network.framework, NetworkConnection, connection diagnostics.