Real integration: Domain Expansion

Checked 2026-10-11. Domain Expansion is an owner-only domain portfolio app on a Cloudflare Worker with Neon Postgres. Its source is the public uppercut-labs/domain-expansion repository. It serves Agent Native capabilities as remote MCP at https://domains.uppercut-labs.com/mcp. This was the first integration outside the repository's fixtures.

What it exercises

Five protected capabilities (domains.list, domains.get, renewals.upcoming, domains.create, domains.update) and a destructive domains.delete with no MCP exposure.
The application's own personal tokens act as the bearer credential and the persisted grant, through bearerAuth, resolveTrustedPrincipal, GrantStorePort and authorizeResource.
Bindings call the application's existing REST services, so validation, revisions, idempotency and rate limits are shared with its API and CLI.

Results

Check	Where	Result
Official SDK client discovery and calls	Deployed	Pass; protocol 2025-11-25
Typed outcomes: found and not found, stale revision, duplicate name	Deployed	Pass
Invalid input rejected before the binding	Deployed	Pass
No token: 401 with `WWW-Authenticate: Bearer`; bad token: 401; foreign Origin: 403 (application check)	Deployed	Pass
A read-only token lists only read tools; a revoked token is refused on the next call	Local, official SDK	Pass
Delete neither listed nor callable	Deployed	Pass
Real host	Deployed	Claude Code 2.1.285 listed the tools and read real data without changes
Rollback to the previous Worker version and back	Deployed	Pass
Other MCP hosts; MCP OAuth	—	Not tested

Findings fixed for 1.0

The integration ran on 0.1.3, and these changes came out of it:

Bindings receive context.caller.
Protected-only servers challenge requests that have no token.
The adapter has onToolFailure and toolName options.
The Zod peer accepts the 4.6.x patch line.
The MCP guide documents the Workers stream lifecycle.

The application was then rebuilt on the packed 1.0 candidate. Its MCP tests and its Worker smoke test under workerd passed. See upgrading from 0.1.x.