Build agentic apps on Rexium
Self-service OAuth, MCP server with semantic action discovery, per-Org schema extensions visible to your agent. Register an app in a minute; your first agent call returns in five.
Why build on Rexium
MCP + tools/search
Your agent discovers actions by intent, not by listing the entire catalog. tools/search ranks Spine actions by relevance, gated by your OAuth scopes.
Spine.3-aware schemas
Per-Org custom fields the merchant declared agent-visible appear inline in /feed.json, in get_product_details, everywhere. Shopify metafields can't do this.
OAuth 2.1 + PKCE + ES256
RFC 8414 metadata discovery, S256 mandatory PKCE, per-Org JWK keypairs for AP2 Cart Mandate signing. Compliance-grade out of the box.
Single-fetch discovery
.well-known/rexium-agent.json per storefront returns capabilities + tools + schemas + signing keys. Your agent walks one URL and knows everything.
Get started in 5 steps
- 1
Sign in
Any Rexium account works. Don't have one yet? (free; no credit card.) - 2
Register your app
Go to the Developer Console. Name + redirect URI + the scopes you want. Get back a client ID and a one-time client secret. - 3
Read the manifest
Fetch{store}/.well-known/rexium-agent.json. You get OAuth endpoints, the MCP server URL, the full scope catalog, schemas, and signing keys. - 4
Authorise a merchant
Send the merchant torexium.ai/oauth/authorizewith PKCE. They click "Allow." You exchange the code at the token endpoint for an access token. - 5
Call MCP
POST JSON-RPC to/mcpServer. Trytools/searchwith your intent — it returns the top-N actions ranked by relevance, filtered by your scopes.
Example: VIP Tagger
~70-line Node.js agent that finds happy customers (5★ review authors in the last 30 days) and tags them as VIP via apply_contact_tags. Audit row in the merchant's /automation dashboard shows "via app vip-tagger" badge.
Dev tier limits
- · Up to 5 apps per developer.
- · Scopes available:
commerce:*,chat:*,reach:*,contacts:*,media:*,meta:read-org.billing:*requires superadmin review. - · Same rate limits as production tier.
- · No SLA; production review available on request.