Is build.arca.mcp/arca-mcp-server up? Live MCP status
It is up, behind a credential. It refused a request carrying no credential with HTTP 401, which is what a server that wants a key or a sign-in does.
It refused without a credential (HTTP 401). A check by URL makes only the initialize request, so it does not walk the OAuth discovery chain; the server's WWW-Authenticate header is in `probe.wwwAuthenticate`. If the server is in the official registry, check it by `name` to learn whether a client can get a credential unattended.
| Outcome | needs_credential |
|---|---|
| HTTP status | 401 |
| Answered in | 106 ms |
| Endpoint checked | https://mcp.arca.build/ |
| Checked |
One MCP handshake with the listed endpoint (server/discover at 2026-07-28, then initialize for a server on the older revision), with no credential and no retry, identifying itself as agentwares-mcp-liveness/0.1 (+https://agentwares-agentcheck.vercel.app/bot). It runs when this page is requested and the result is reused for 10 minutes, so the time above is when it was taken.
Live status every few hours: Wellknown
Sign-in
Sign-in is broken. Sign-in breaks at "Metadata `issuer` is identical to the advertised authorization server", and the fix is the identity provider's.
First broken step: Metadata `issuer` is identical to the advertised authorization server, the identity provider’s to fix. issuer=https://rapid-pole-17.authkit.app vs https://rapid-pole-17.authkit.app/ (they differ only by a trailing slash or case, which strict clients still reject)
Fix: Make `issuer` in the metadata exactly the URL listed in the protected-resource metadata's authorization_servers (https://rapid-pole-17.authkit.app/), character for character, or list exactly the issuer the metadata states. (RFC 8414 ยง3.3; MCP 2026-07-28 "Authorization Server Metadata Discovery")
- claude.ai: blocked — Metadata `issuer` is identical to the advertised authorization server: issuer=https://rapid-pole-17.authkit.app vs https://rapid-pole-17.authkit.app/ (they differ only by a trailing slash or case, which strict clients still reject)
- Claude Code: blocked — Metadata `issuer` is identical to the advertised authorization server: issuer=https://rapid-pole-17.authkit.app vs https://rapid-pole-17.authkit.app/ (they differ only by a trailing slash or case, which strict clients still reject)
- ChatGPT: blocked — Metadata `issuer` is identical to the advertised authorization server: issuer=https://rapid-pole-17.authkit.app vs https://rapid-pole-17.authkit.app/ (they differ only by a trailing slash or case, which strict clients still reject)
- VS Code: blocked — Metadata `issuer` is identical to the advertised authorization server: issuer=https://rapid-pole-17.authkit.app vs https://rapid-pole-17.authkit.app/ (they differ only by a trailing slash or case, which strict clients still reject)
- Cursor: blocked — Metadata `issuer` is identical to the advertised authorization server: issuer=https://rapid-pole-17.authkit.app vs https://rapid-pole-17.authkit.app/ (they differ only by a trailing slash or case, which strict clients still reject)
Discovery only, from the challenge this server sent the check above: no credential, no client registration. Client verdicts are emulated from each client’s published requirements. Steps, documents and redirect URIs: the full sign-in report. Watch it hourly: agentcheck's free watch checks this server every hour, follows the sign-in a new client follows with these same rules, and emails when a step breaks; no account. Nightly, with history: mcpcheck Server Pro re-runs these sign-in checks against the server every night, with 90 days of history, and emails when one fails ($49 a server a month; the first run is free).
Email me when this server changes
That was one look. To hear when it stops answering or its tools change, leave an address.
Free, no password or GitHub: one confirmation email first, then a check every hour and an email when it stops answering or its tools change. Every email has a link to stop. More about it.
Monthly census, 6 October 2026
The census sends the same request to every remote listing in the official registry once a month. On 6 October 2026 this one was not an MCP server at that address (The operation was aborted due to timeout). Every listing’s result: index.ndjson (what the files hold: index.meta.json).
Agent discovery documents at this origin
Not asked on 9 October 2026: the census could not connect to any listing at https://mcp.arca.build. Who publishes them.
Tool changes between snapshots
It is not in the 2026-10 snapshot. Snapshots record the tool list of every listing that answered a stock client with no credential in that month’s census.
Which tools were added or removed, and whose description or schemas changed, from content hashes in the monthly snapshots. Per tool, as JSON: /v1/drift.
The listing
| Registry name | build.arca.mcp/arca-mcp-server |
|---|---|
| Title | Arca |
| Description | Arca is a private data vault where your AI stores your structured data, semantic memory and skills. |
| Endpoint | https://mcp.arca.build |
| Other endpoints | https://mcp.arca.build |
| Publisher repository | none listed |
| Version | 0.0.1 |
| Listing updated |
Also
The full check by name, as JSON (on a 401 it also follows the OAuth discovery chain) · Watch it · Check another server · llms.txt