Amazon SP-API and operations automation developer for a sellable agency software suite

We are a UK agency that manages Amazon Seller Central and Vendor Central accounts for consumer brands, including international brands entering the UK, EU, USA and Canada. We are building our own operating system for running many Amazon accounts. We use it ourselves first and may license it to other agencies later. We only build what existing tools miss and connect proven tools for the rest. Our AI model throughout is Claude, via the Claude API. We need one experienced developer for the whole build. The project starts in January 2027 and runs up to nine months. Right now we need a detailed quote only. Work starts once our funding is confirmed. WHAT TO BUILD 1. Amazon data layer - Build on our existing SP-API app, registered as a public developer in Amazon's Solution Provider Portal. No rented data pipeline - Clients authorise via Amazon's OAuth website flow. Store one refresh token per selling account per region securely - Seller Central and Vendor Central authorise separately and use different reports (Sales and Traffic and FBA inventory versus Vendor Retail Analytics) - Correct regional endpoints (North America, Europe incl. UK, EU, Middle East and India, Far East) and marketplace IDs - Reports API and Data Kiosk on a schedule within rate limits. No restricted roles or customer PII. Built to Amazon's Data Protection Policy - Amazon Ads API, equal priority. Own approval, Login with Amazon consent, profile per marketplace. Daily Sponsored Products, Brands and Display reports down to search term, joined to sales for TACoS and organic versus paid 2. Unified stock view - We only work with 3PLs that offer an API. Connect by API to the systems UK 3PLs run on (Mintsoft, Linnworks, Unleashed) and to direct 3PL APIs. First partners Pick Pack N Post and Blue30 - FBA, Vendor and 3PL stock in one view per brand and SKU, with days of cover and reorder alerts. No full forecasting engine 3. Profit per SKU - Amazon fees, ad spend, cost of goods and landed cost per product and client - We currently use Sellerboard. Import or reconcile against Sellerboard data where possible 4. Listing and account health - Daily checks for suppressed listings, Buy Box losses, unauthorised sellers, account health warnings, and Vendor chargebacks and shortages - Fixes drafted by Claude for a person to approve. Keepa API for price, rank and Buy Box history 5. Marketplace expansion - Claude translates listings and runs readiness checks when a client launches in a new EU or North American marketplace, approved before going live 6. Onboarding handover - When a new client's stock is booked into a 3PL, start onboarding automatically. Amazon authorisation request, Freedcamp tasks, Xero and GoCardless billing set-up, and adding the brand to dashboards 7. Client dashboards, newsletters and approval layer - Central database in BigQuery or Google Sheets (you advise), built so the front end can be replaced later - Looker Studio dashboard per client, based on our existing client tracker (shared after hire) covering product performance, weekly PPC, monthly sales targets, and MoM and YoY comparisons. Same content, far more visual and easier to read - A short newsletter for each client each period, written by Claude and co-branded in the client's brand style and ours using our existing design templates. Sent by each client's preferred channel, such as email, WhatsApp or Excel - Claude drafts recommendations and replies to WhatsApp (Twilio), Gmail and Tactiq action points, routed to Freedcamp via Make. Nothing is sent or changed until a person approves it CURRENT TOOLS Google Workspace, Make, Freedcamp, Sellerboard, Keepa, Data Dive, Twilio, Claude, Xero, GoCardless, Tactiq, Canva, Seller Central and Vendor Central. DEFINITION OF DONE - Each module runs live on real client accounts for two weeks without errors - All code, logins and infrastructure in our own accounts, with full intellectual property assigned to our company - Written documentation and a recorded walkthrough of every module - Monthly running costs listed and agreed before build YOUR PROPOSAL SHOULD INCLUDE - A fixed price for each of the seven modules - Hours and timeline per module - Your recommended stack and monthly running cost - A monthly price for maintenance after handover - Two examples of similar SP-API or Ads API work - A written, dated quote we can share with our funder