Amazon seller MCP server for Claude ships free, with two anti-hallucination lessons
Fap_Jesus · reddit · 2026-09-23
The founder of an Amazon software company built an MCP server over their own API: connect once and Claude can read live Seller Central and Ads data — account health (AHR, order defect rate, late shipment), FBA inventory, reimbursements already paid, still-claimable discrepancies, plan-of-action cases, tracked keywords, listing audit scores and campaigns. The read-only version is free; write permissions (e.g., adjusting ad bids) are coming.
Two lessons for anyone building similar MCP servers:
- Annotate every tool. Claude groups annotated tools into "Read-only tools" and can auto-run them without per-call prompting; missing hints get read tools treated like writes.
- Allow "I don't know" in tool output. Their server refuses to show unverifiable numbers instead of estimating — that single decision removed most hallucination risk by leaving the model nothing to round off.
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