{"slug": "the-api-worked-the-payload-didnt", "title": "The API worked. The payload didn’t.", "summary": "A developer built BandwidthGuard, a free browser-based tool that analyzes JSON payloads to identify unnecessary data bloat in API responses. The tool provides field-level breakdowns, compression comparisons, and prompts for AI coding agents to help slim down serializers. It was created after the developer noticed that AI-generated endpoints often return far more data than needed, with gzip compression masking the issue.", "body_md": "I kept shipping APIs I hadn’t really looked at.\n\nI’d ask whatever assistant was open Cursor, Claude, Antigravity, Trae for a users endpoint. It generated the route, the DTO, the response. The page rendered. I moved on.\n\nThen I opened DevTools → Network.\n\nGzip made the response look small, so I ignored it.\n\nThat was the mistake.\n\nThis is not only a backend problem. Frontend apps consume these payloads too.\n\nIf the client receives something like 500KB and only needs 50KB, both sides pay for it, whether the contract was written by you, your team, or an agent.\n\nCompression hides sloppy JSON. It doesn't delete fields you shouldn't have sent.\n\nA normal-looking user list I ran through this looked like:\n\n`preferences` object repeated on every row: 528 B\nThen Gzip crushed it to a few hundred bytes. That’s how this survives code review. The wire looks fine. The shape is still fat.\n\nI didn’t want a place where I paste a giant JSON blob and stare at charts.\n\nI wanted the same agent that wrote the endpoint to look at it and say: we don’t need all this.\n\nSo I built [BandwidthGuard](https://bandwidthguard.chidkoli.com/).\n\nTwo ways in.\n\nGo to [/analyze](https://bandwidthguard.chidkoli.com/analyze).\n\nPaste JSON, drop a HAR, or paste cURL. It stays in the browser. Nothing gets uploaded.\n\nYou get a score, a field-level breakdown, Gzip / Brotli / Zstd / MessagePack / CBOR on that payload, and fixes split into:\n\nThat last split matters more than the codec table. Minifying JSON is easy. Pulling email off a list endpoint is not the same kind of change.\n\nThis is the path I actually use when I just generated the endpoint.\n\nOn the homepage, open **Feed Payload Insights into Your AI Coding Agent**.\n\n`GET /v1/users` or just `User list`\nThe prompt already tells the agent to find bloat, clean the serializer, compare compression, show before/after, and check work in the analyzer. It also points to [`/llms.txt`](https://bandwidthguard.chidkoli.com/llms.txt) so the model isn’t inventing a process.\n\nGenerate → inspect one payload, or skip straight to the prompt → slim the serializer → paste the new response back if you want proof.\n\nIt is not an APM.\n\nIt is not your cloud invoice.\n\nIt will not cut a bill by some fixed percentage just because Gzip exists.\n\nIf compression is already on, the useful win is structural: stop sending unused fields.\n\nUse a list endpoint you didn’t hand-write. Detail endpoints are usually less embarrassing.\n\nThen look at two things only:\n\nFree. No account. Runs in the tab.\n\n[https://bandwidthguard.chidkoli.com/](https://bandwidthguard.chidkoli.com/)\n\nI built this because I got tired of shipping apps that worked and still moved more data than they needed.\n\nCover image: the 5:2 two-card graphic (agent-cards-5x2-wide.jpg).", "url": "https://wpnews.pro/news/the-api-worked-the-payload-didnt", "canonical_source": "https://dev.to/avi_natani_732ee2ebef2121/the-api-worked-the-payload-didnt-1nhe", "published_at": "2026-09-07 04:28:00+00:00", "updated_at": "2026-09-07 04:57:54.692345+00:00", "lang": "en", "topics": ["developer-tools", "ai-tools"], "entities": ["BandwidthGuard", "Cursor", "Claude", "Antigravity", "Trae"], "alternates": {"html": "https://wpnews.pro/news/the-api-worked-the-payload-didnt", "markdown": "https://wpnews.pro/news/the-api-worked-the-payload-didnt.md", "text": "https://wpnews.pro/news/the-api-worked-the-payload-didnt.txt", "jsonld": "https://wpnews.pro/news/the-api-worked-the-payload-didnt.jsonld"}}