Circleback: MCP server, CLI and agent surfaces

Sign-in required, tools not seen, not counted. The MCP endpoint listed for Circleback at circleback.ai answered 401 with OAuth metadata on 4 November 2026. Its tools can be listed only after a person authorizes a client, and this directory never signs in.

Fact sheet

Company	Circleback
Domain	circleback.ai
Category	Productivity (Ora leaderboard category)
MCP server	Sign-in required (OAuth with client registration)
Ora score	76, grade B; Ora scanned the domain on 26 October 2026 and the cached score was read on 5 November 2026 from Ora's leaderboard (Ora's score page for circleback.ai, a vendor-published score)
Company found through	the awesome-remote-mcp-servers list; the official MCP Registry; Ora's public leaderboard
Last verified	4 November 2026

MCP server

Endpoint	`https://circleback.ai/api/mcp`
How it was found	listed in the awesome-remote-mcp-servers list; the official MCP Registry; Ora's public leaderboard
Transport	streamable-http
HTTP status	401
Connected	4 November 2026, 20:02 UTC
Handshake time	1,023 ms over 1 attempt

The endpoint answered the handshake with a sign-in challenge, so the tool list is not visible to this directory. It is not counted as an MCP server: a sign-in challenge is its own state, and the connector listed no tools.

Connector log

2 connections on 4 November 2026, read-only methods only

19:56:53Z https://circleback.ai/api/mcp sent initialize result auth-required (HTTP 401) 1106 ms
20:02:25Z https://circleback.ai/api/mcp sent initialize result auth-required (HTTP 401) 1023 ms

Authentication

Auth type	OAuth with client registration
What the challenge said	`Bearer realm="OAuth", resource_metadata="https://circleback.ai/.well-known/oauth-protected-resource/api/mcp", scope="user user:write"`
Protected resource metadata	circleback.ai
Authorization server metadata	circleback.ai
Registration endpoint	`https://circleback.ai/api/oauth/register`
Auth as listed by a registry	OAuth2.1 (a claim, not checked by connecting)

The sign-in route, step by step

Request https://circleback.ai/api/mcp without a token. It answers 401 and a WWW-Authenticate header.
Read the protected resource metadata at https://circleback.ai/.well-known/oauth-protected-resource/api/mcp to find the authorization server.
Register a client at the registration endpoint https://circleback.ai/api/oauth/register (dynamic client registration), so no human has to create an app first.
Send a person through the authorization page, then retry the endpoint with the bearer token. The connector stops after step 2 and never authorizes.

See OAuth for MCP: client ID metadata documents and dynamic registration for how each route works.

CLI

No CLI is on record for Circleback. The directory checks a package only where a source names one, so this is a floor: a company can ship a command line that no source read for this edition mentions. See shipping a CLI agents can use.

Other agent surfaces

Agent surfaces other than MCP and CLI
Surface	Result
OpenAPI file	No OpenAPI file at the root paths checked.
WebMCP in the initial HTML	Not detected on the home page by the shared crawl.
MCP discovery file	Not found (the crawl got a non-200 answer).
A2A agent card	Not found (the crawl got a non-200 answer).
A2A agent card (older path)	Not found (the crawl got a non-200 answer).
agents.json	Not found (the crawl got a non-200 answer).
OAuth authorization server metadata	Found: circleback.ai/.well-known/oauth-authorization-server answered with a valid document in the shared crawl.
NLWeb endpoint	Not checked in this edition.

Registry listings

Registry listings
Registry	Listed
Official MCP Registry	Yes: ai.circleback/circleback
GitHub MCP Registry	No
awesome-remote-mcp-servers	Yes
Smithery	Not checked: Smithery's listing pages and search API were unavailable on 4 November 2026.
Glama	Not checked: Glama's API needs a key and attribution terms.