20 KiB
Platform Research
https://docs.google.com/spreadsheets/d/1xWfXn-wbiHTBeqyhnq0b46_sgLGyiYc_5N5mXKYD1R8/edit?gid=0#gid=0
| Platform | Order Event: placed | Order Event: changed | Products List | Products Look up | Inventory Look up | Inventory Update | Inventory Event: change |
|---|---|---|---|---|---|---|---|
| Etsy (live) | N/A — no webhook/push system in API v3 at all; poll GET /v3/application/shops/{shop_id}/receipts (filter min_created) |
poll same endpoint filtered by min_last_modified |
GET /v3/application/shops/{shop_id}/listings |
GET /v3/application/listings/{listing_id} |
GET /v3/application/listings/{listing_id}/inventory |
PUT /v3/application/listings/{listing_id}/inventory |
N/A — no inventory-change webhook; poll the inventory endpoint |
| Shopify | orders/create | orders/cancelled, orders/delete, orders/paid, etc | /queries/products | /queries/product | /queries/product | /mutations/inventorySetQuantities | inventory_levels/update |
| WooCommerce | webhook order.created |
webhook order.updated, order.deleted |
GET /wp-json/wc/v3/products |
GET /wp-json/wc/v3/products/<id> |
stock_quantity field on product resource |
PUT /wp-json/wc/v3/products/<id> (stock_quantity), or /products/batch |
product.updated (no dedicated inventory webhook) |
| BigCommerce | webhook store/order/created |
webhook store/order/updated, store/order/statusUpdated |
GET /v3/catalog/products |
GET /v3/catalog/products/{product_id} |
GET /v3/inventory/items |
PUT /v3/inventory/adjustments/absolute (also /relative) |
store/product/inventory/updated |
| Wix | webhook wix.ecom.v1.order.created |
webhook wix.ecom.v1.order.updated (also .canceled) |
Query Products (Catalog V3) | Get Product | Query Inventory Items | Update Inventory Variants | wix.stores.catalog.v3.inventory_item.updated |
| Squarespace | webhook order.create |
webhook order.update (FULFILLED, REFUNDED, CANCELED, MARKED_PENDING, EMAIL_UPDATED) |
GET /v2/commerce/products |
GET /v2/commerce/products/{productIdCsvs} |
GET /1.0/commerce/inventory/{variantIdCsvs} |
POST /1.0/commerce/inventory/adjustments |
N/A (no inventory webhook topic) |
| Square Online | webhook order.created |
webhook order.updated, order.fulfillment.updated |
GET /v2/catalog/list |
GET /v2/catalog/object/{object_id} |
POST /v2/inventory/counts/batch-retrieve |
POST /v2/inventory/changes/batch-create (BatchChangeInventory) |
webhook inventory.count.updated |
| Zoho | webhook salesorder.created (Zoho Commerce) |
webhook salesorder.confirmed, .cancelled, .declined, .shipped, .delivered |
GET /store/api/v1/products |
GET /store/api/v1/products/{product_id} |
GET /store/api/v1/variants (stock_on_hand, actual_available_stock) |
POST /store/api/v1/inventoryadjustments |
N/A (no inventory/stock webhook event) |
| Ecwid | webhook order.created |
webhook order.updated, order.deleted |
GET /api/v3/{storeId}/products |
GET /api/v3/{storeId}/products/{productId} |
GET /api/v3/{storeId}/products/{productId} (quantity/unlimited) |
PUT /api/v3/{storeId}/products/{productId}/inventory (quantityDelta) |
product.updated webhook |
| Big Cartel | webhook order.create (app-approved) |
webhook order.update (app-approved) |
GET /v1/accounts/{account_id}/products |
GET /v1/accounts/{account_id}/products/{id} |
N/A — no dedicated inventory field/endpoint | N/A — no inventory update endpoint | N/A — no inventory-specific webhook |
| Amazon | ORDER_CHANGE notification (SP-API) |
ORDER_CHANGE notification (same type, status delta) |
searchCatalogItems (GET /catalog/2022-04-01/items) |
getCatalogItem (GET /catalog/2022-04-01/items/{asin}) |
getInventorySummaries (FBA Inventory API, GET /fba/inventory/v1/summaries) |
patchListingsItem (PATCH /listings/2021-08-01/items/{sellerId}/{sku}) |
FBA_INVENTORY_AVAILABILITY_CHANGES notification |
| Walmart Marketplace | PO created event (webhook) | Order intent to cancel / PO line auto-cancelled event (webhook); status flow Created→Acknowledged→Shipped→Delivered/Cancelled | GET /v3/items (getAllItems) |
GET /v3/items/{id} (getAnItem) |
GET /v3/inventory?sku={sku} |
PUT /v3/inventory (also bulk via POST /v3/feeds) |
Inventory OOS event (webhook) |
| Ebay | FixedPriceTransaction / ItemSold (Platform Notifications, legacy Trading API) |
ItemMarkedShipped notification; also getOrders filtered by lastmodifieddate (Fulfillment API) |
GET /sell/inventory/v1/inventory_item (getInventoryItems) |
GET /sell/inventory/v1/inventory_item/{sku} (getInventoryItem) |
GET /sell/inventory/v1/inventory_item/{sku} (availability.shipToLocationAvailability) |
POST /sell/inventory/v1/bulk_update_price_quantity (bulkUpdatePriceQuantity) |
N/A — no dedicated inventory-change topic found |
Notes / caveats from research
- Square Online: no separate API — orders, catalog, and inventory are handled by Square's core Seller APIs (developer.squareup.com), the same ones used across all Square products. Unrelated to Squarespace despite the name.
- Zoho: "Zoho Commerce" (commerce.zoho.com) is the storefront product comparable to Shopify/Squarespace and owns the order/product/webhook APIs listed above. Zoho Inventory is a separate warehouse/stock-management app with its own API but no documented webhook support.
- Big Cartel: no true inventory API — only an
inventory_enabledflag andquantity_gte/quantity_ltefilters on products. No endpoint to set stock and no inventory-change webhook. Webhook access is gated per-app approval; exact topic names are inferred from integration examples since Big Cartel has no canonical published list. - Amazon SP-API: no separate "placed" vs "changed" order topics — both flow through a single
ORDER_CHANGEnotification, differentiated by payload content. - WooCommerce / Ecwid: neither has a dedicated inventory-change webhook; stock changes surface via the general
product.updatedevent instead. - Etsy: the one row in the first table sourced from this repo's actual code rather than external docs (
domains/platforms/etsy/generated_client, generated from Etsy's own OpenAPI spec) - so it's the most reliable row here, not the least. Etsy Open API v3 has no webhook/push system whatsoever for anything, order or inventory alike; every other platform in the table has at least some real-time push. The live integration in this repo currently only implements the OAuth connection flow (GenerateConnectionURLForNewAccount/HandleNewAuthCodeindomains/platforms/etsy/etsy.go) - polling-based order/inventory sync againstGetShopReceipts/GetListingInventoryisn't built yet. - Ebay: order-event names are less certain — developer.ebay.com pages repeatedly failed to load during research, so those values come from documented Platform Notifications event types found via search rather than a directly confirmed doc page.
- TikTok Shop: not in the capability table above -
partner.tiktokshop.com/docv2is JS-rendered and didn't return usable content via fetch, so exact webhook event names and endpoint paths aren't confirmed (unlike every other row in that table, which comes from readable docs). What is confirmed via secondary sources: TikTok Shop's Partner API has webhooks covering order, product, and inventory changes, and a Product/Inventory API for listing and stock management. Treat as directionally real but needing its own dedicated research pass - with confirmed endpoint names - before implementation. - BigCommerce vs Tiktok: the capability table above includes BigCommerce, but BigCommerce is not one of this codebase's actual mock platforms (see
AGENTS.md's platform list -domains/accounts/platform.go'sallPlatformshasTiktok, not BigCommerce). BigCommerce's row is left in place since the research itself may still be useful, but it's excluded from the priority ranking below; Tiktok is included despite the weaker sourcing noted above, since it's a platform that actually exists in this codebase.
Market-size research (2026-08-20)
Pulled to sanity-check which platforms are most worth integrating first, on
top of the API-completeness comparison above. See AGENTS.md's "Platform
integration priority" section for the resulting ranking and reasoning.
Figures are mid-2026 estimates for FY2025 (or most recent trailing period) unless noted. Anything not sourced from an SEC filing is a third-party estimate (StoreLeads, DemandSage, Marketplace Pulse, etc.) and should be treated as directional, not precise - methodology varies a lot between sources, especially for "number of stores/sellers."
| Platform | Active sellers/stores | Most recent GMV | Source confidence |
|---|---|---|---|
| Amazon (3P) | ~1.9M active sellers | ~$575B (3P GMV, 2025); total Amazon GMV >$800B | Moderate - earnings-adjacent estimates |
| Shopify | ~3-6.8M active stores (methodology varies) | $378.4B (FY2025, +29% YoY) | High - SEC filings |
| eBay | ~18.3M active sellers | $79.6B (FY2025, +7% YoY) | High - SEC filings |
| Etsy (already live) | 5.6M active sellers | $11.92B GMS (FY2025, -5.3%) | High - SEC filings |
| Squarespace Commerce | ~353K live ecommerce sites | ~$7.2B (2026 est.) | Low - marketing estimate |
| WooCommerce | ~4.2-6M active stores | ~$30-35B (2025 est.; average store is tiny, ~$7-8K/yr) | Low - third-party estimate, no central ledger |
| Walmart Marketplace | ~200-250K sellers, +50% YoY growth | ~$10B (rough external estimate; Walmart doesn't break this out cleanly) | Low |
| Wix eCommerce | ~760K-3M live stores | $4.1B-$12.4B (conflicting self-reported figures) | Low |
| Tiktok Shop | ~15M sellers globally, ~500K registered / ~216K active in the US | $64.3B global (2025, nearly 2x 2024); $15.1B US (+68% YoY) | Low - third-party estimate, hypergrowth market |
| BigCommerce (not an actual mock platform here - see caveat above) | ~37-42K active stores (shrinking, shifting to enterprise) | $34B+ | Moderate |
| Square Online | n/a (bundled into Square's overall $250B GPV, mostly in-person POS) | Can't isolate | N/A |
| Zoho Commerce | ~2,196 stores globally (285 US), +34% YoY US growth off a tiny base | Not disclosed; likely small given store count | Low |
| Ecwid | ~130-164K live stores, declining (-20% YoY) | Not disclosed | Low |
| Big Cartel | ~91-192K stores (estimates vary widely), declining sharply (-41% YoY in 2026 Q1) | Not disclosed; platform targets low-AOV indie sellers | Low |
Key takeaways:
- Amazon's 3P GMV ($575B) is ~1.5x Shopify's total GMV despite Shopify having 2-3x more active stores - Amazon sellers skew toward larger, more serious operations.
- eBay has by far the most sellers (18.3M) but the lowest GMV-per-seller of any major platform here ($79.6B / 18.3M), suggesting a lot of integration surface for comparatively thin per-seller value - compounded by its weak inventory-webhook story (see table above).
- WooCommerce can't be sized financially at all - it's a WordPress plugin, not a company with a ledger - so its case rests entirely on raw store count, not proven revenue-per-integration.
- Walmart Marketplace is small in absolute terms but growing fast (+50% YoY) and is a natural "second marketplace" for sellers already on Amazon.
Weighted priority ranking (2026-08-20)
Scores each of the 12 not-yet-live mock platforms (everything in
domains/accounts/platform.go's allPlatforms except Etsy) on four 0-10
criteria, weighted and summed to a single composite score. This is a
judgment call turned into numbers, not a precise formula - the weights and
per-platform scores below are my read of the research above; treat the
ranking as the useful output, not the second decimal place. BigCommerce is
excluded (not an actual platform in this codebase, see caveat above).
Etsy itself is scored too, as a reference row only - it's already the live integration, so it's not competing for "what to build next," but running it through the same rubric is a useful sanity check on the model.
Criteria & weights:
- GMV / market opportunity (45%) - bucketed from the GMV figures above (>$500B=10, $300-500B=9, $50-100B=7, $25-50B=6, $8-15B=4, $5-8B=3, undisclosed-and-small=1). This is weighted highest because "lucrative" is fundamentally a dollar-opportunity question.
- API/inventory-sync completeness (30%) - from the capability table at the top of this doc: full order-webhook + dedicated inventory-webhook coverage scores highest, missing inventory webhook scores mid, no inventory API at all (Big Cartel) scores near-zero. This directly gates how good a product experience is even possible on that platform.
- Growth trajectory (15%) - YoY GMV/store growth; rewards fast-growing platforms (Tiktok, Walmart) and penalizes shrinking ones (Ecwid, Big Cartel) as a proxy for where future opportunity is heading.
- Integration cost, inverted (10%) - auth complexity and existing
codebase head start (Amazon's
domains/amazonbackground-processor infra) score higher; gated/undocumented webhook access (Big Cartel) scores lowest. Weighted lowest since it affects timeline more than whether the integration is worth doing at all.
Scores:
| Platform | GMV (45%) | API (30%) | Growth (15%) | Cost (10%) | Weighted total |
|---|---|---|---|---|---|
| Shopify | 9 | 10 | 8 | 9 | 9.15 |
| Amazon | 10 | 10 | 5 | 6 | 8.85 |
| Tiktok Shop | 7 | 7 | 10 | 4 | 7.15 |
| Walmart Marketplace | 4 | 9 | 9 | 5 | 6.35 |
| Wix | 4 | 10 | 5 | 8 | 6.35 |
| WooCommerce | 6 | 6 | 5 | 7 | 5.95 |
| Square Online | 3 | 10 | 5 | 8 | 5.90 |
| Ebay | 7 | 5 | 4 | 5 | 5.75 |
| Squarespace | 3 | 6 | 6 | 7 | 4.75 |
| Etsy (reference, already live) | 4 | 3 | 1 | 10 | 3.85 |
| Zoho | 1 | 6 | 6 | 7 | 3.85 |
| Ecwid | 1 | 6 | 1 | 8 | 3.20 |
| Big Cartel | 1 | 2 | 1 | 3 | 1.50 |
Ranked priority order:
- Shopify — 9.15
- Amazon — 8.85
- Tiktok Shop — 7.15
- Walmart Marketplace — 6.35
- Wix — 6.35 (behind Walmart on the growth tiebreaker: 9 vs 5)
- WooCommerce — 5.95
- Square Online — 5.90
- Ebay — 5.75
- Squarespace — 4.75
- Etsy — 3.85 (reference only - already live, not competing for "what to build next")
- Zoho — 3.85
- Ecwid — 3.20
- Big Cartel — 1.50
Notable movement from the earlier qualitative pass: Shopify edges out Amazon once integration cost and growth are counted, not just raw GMV - Amazon's dollar opportunity is still bigger, but Shopify is cheaper to build, easier to get first customers through (App Store), and still growing faster. Tiktok Shop, unresearched until this pass, lands at #3 on the strength of its growth rate alone - but see the sourcing caveat above before acting on that; its API details need a dedicated research pass before it's actually buildable. Big Cartel is unambiguously last: no inventory API is a structural dealbreaker for this specific product, independent of its market size.
Etsy, run through the same rubric, scores 3.85 - tied with Zoho, below every platform except Ecwid and Big Cartel. Its GMV is mid-pack and declining (-5.3% YoY), and - per the caveat above - it's the only platform researched with literally no webhook/push mechanism for anything, so it scores below every platform here except Big Cartel on API completeness too. The only criterion where it dominates is integration cost (10/10, since it's already built). This is a useful gut-check on the model, not a claim that building Etsy first was a mistake - Etsy was presumably chosen for reasons this rubric doesn't capture (an existing relationship, a founder's market knowledge, being the most approachable API to get developer credentials for), not for having the best growth/GMV/webhook profile. Worth remembering when weighing this ranking against Etsy's actual day-to-day integration cost, which - per the caveat above - has turned out to be nontrivial in practice: with no webhooks at all, real order/inventory sync has to be built as a polling loop, which is exactly the kind of integration cost this rubric's "Cost" column doesn't capture once a platform is more than superficially wired up.
Sources:
- Shopify Statistics 2026: Market Share, $116B GMV, Employees
- Shopify 2026: $378.4B GMV, Store and Seller Data
- Amazon Third-Party Sellers Generate $575 Billion in GMV
- Amazon GMV Surpassed $800 Billion in 2025 - Marketplace Pulse
- Top 1.6% of Sellers Drive 50% of Amazon's 3P GMV
- WooCommerce Market Share 2026: 33.4% Global Stats
- BigCommerce Statistics 2026
- How many Walmart Marketplace sellers are there in 2025?
- Walmart Marketplace Grows 50% in One Year - Marketplace Pulse
- eBay Gross Merchandise Volume (GMV) 2018-2026 - Marketplace Pulse
- eBay Statistics (2026): Active Buyers, Listings, GMV, Revenue
- The State of Wix in 2026
- Squarespace Subscriber and Revenue Statistics for 2026
- Etsy, Inc. Reports Fourth Quarter and Full Year 2025 Results
- Block Statistics (2026): Sellers, GPV, Block Revenue