How Muse Connectors Work, and How to Build One

Muse connectors are how the Muse agent reaches outside services. There are two kinds: directory connectors, which businesses submit at muse.ai/platform and Meta reviews, and custom connectors, which Muse writes for a single user from any API, storing the credentials in its secure vault. To build one today, you either publish a clean API (usually an OpenAPI spec or MCP server) that Muse can wire up as a custom connector, or apply to the directory and go through Meta's functional, security and legal review.

Directory connectors vs custom connectors

	Directory connector	Custom connector
Who builds it	A business, via muse.ai/platform	Muse, for one user, on request
Reviewed by Meta	Yes: functional, security, legal, end-to-end tests	No
Who sees it	Every user, in the connector directory	Only that user
Credentials	Handled through the connector	Muse's Secure Credentials Store

Sources: Meta help, CellCog.

Facebook, Instagram and Threads are a third case: they connect automatically if they share your Accounts Center. Many connectors can also be set to read-only, so Muse retrieves data but can't act. You can disconnect any of them under Settings, then Connectors.

Meta's warning on custom connectors is blunt: "Meta doesn't review custom connectors or how they use your information, so grant access with caution."

Which connectors exist today

At launch on September 8, Meta listed Gmail, Google Calendar, Google Docs, Outlook, Plaid, Stripe Link, Shopify Catalog, OpenTable, Ticketmaster, Function Health, HealthEx, Withings, Peloton, Duffel and Tailscale. PostFast keeps a sourced full list. Partner write-ups in the catalog include Plaid (12,000+ US institutions), Duffel (500+ airlines), Spotify, HealthEx and Instacart.

At Connect on September 23, Meta announced more: Walmart, Best Buy, Sephora, Wayfair, Shop Pay, PayPal, Expedia, Notion, Granola, GitHub, Box and others.

How a custom connector gets built

You ask Muse to connect to a service, and it does the integration work itself inside its VM. David Singleton showed Muse writing and running its own integration code in the user's cloud VM, and a Reddit demo has it building a Linear connector in under a minute from an API key.

AdaptlyPost's walkthrough is the clearest recipe:

1. Give Muse the public OpenAPI spec URL and a docs link.
2. Tell it the auth format (Authorization: Bearer <token>) and a safe first call ("call GET /social-accounts first, don't publish anything yet").
3. Paste the token into Muse's secure credential prompt, not the chat.
4. Muse fetches the spec, writes client code, makes the test call and shows you the result.

MCP works too. Postiz shows how to hook its OAuth MCP server into Muse through the custom-connector path, and Threadwell bridges to Slack's official MCP server. For the difference between the two, see MCP servers vs Muse connectors.

Why the credentials stay safe (in theory)

Custom connector code runs inside the Muse Secure VM, but it never sees your real token. Meta's security post describes credential surrogation: code gets a surrogate token minted by a host service, and Sentinel swaps in the real credential at the network boundary. Sentinel is also "the sole permission authority" for connector actions and all network egress. Connector code is managed by a separate privsep service outside the agent's container.

Community connectors follow the same idea. The Tailscale skill and GitHub skill keep tokens in the vault and attach them through a runtime surrogate. Details in what the Muse Secure VM is.

Building a connector for other users

If you run a service and want everyone on Muse to use it, the platform has three steps (muse.ai/platform):

1. Describe your product: what the connector does and how users will use it.
2. Submit for review: Meta checks "functional, security, and legal requirements" and runs end-to-end tests.
3. Appear in the directory: approved connectors are listed, with possible editorial featuring.

Stripe Link is the payments rail for connectors that sell things. Meta received more than 1,500 applications in under a week, per TechCrunch.

What's missing: as of September 18, CellCog found no published SDK, API spec, developer terms, fee structure, revenue share or review timeline. The form asks for a product description, not code. Plan for that uncertainty.

Patterns builders use

Without an official spec, builders converged on a few shapes. From the tools and apps category:

• Serverless gateway with one bearer token. The Cloudflare Workers starter keeps upstream API keys server-side behind a single token, with an OpenAPI spec, a SKILL.md template and a proof checklist.
• Registry-generated routes. AstroxNetwork's Apache-2.0 template generates routes, OpenAPI and llms.txt from one registry, with per-connection tokens and async jobs.
• Small-business actions. The HVAC and plumbing connector quotes a visit, holds a slot, books the job and sends a deposit link.
• Hold-and-approve. Change Verifier runs seven checks on payee bank changes and holds them until a named owner accepts.
• Read-only data. Dowser surfaces settlements, recalls and unused credits, and barbaros-mcp serves a privacy dataset.
• Reaching your own machines. muse-fileapi and the Mac menu-bar connector expose local files over a Cloudflare tunnel with whitelists and audit logs.

Collections like 150 one-paste connector skills and the awesome-muse-connectors catalog are worth reading for conventions, but they're unreviewed. Read the code before you paste anything that asks for a token.

Practical tips

• Start read-only. Add write actions once you've watched a few runs.
• Give Muse a harmless first call to verify auth.
• Declare allowed hosts and keep scopes narrow.
• Make destructive actions two-phase (propose, then confirm), like muse-fileapi's writes.
• Publish an llms.txt or clear docs page; Muse reads them when writing the client.

Built one? Submit it to the catalog.

Frequently asked questions

What is a Muse connector?

It's an integration that lets the Muse agent read from or act in another service, like Gmail, Plaid or Spotify. Directory connectors are reviewed by Meta; custom connectors are built by Muse for one user and aren't reviewed.

How do I add a custom connector to Muse?

Ask Muse to connect to the service, give it the API docs or OpenAPI spec, and paste the API key into the secure credential prompt when asked. Muse writes the client code in its VM and runs a test call.

How do I get my connector listed in the Muse directory?

Apply at muse.ai/platform. Meta reviews submissions for functional, security and legal requirements and runs end-to-end tests before listing. Fees, revenue share and review timelines haven't been published.

Does Muse support MCP servers?

Builders have connected MCP servers, such as Postiz's OAuth MCP server and Slack's official MCP server, through the custom-connector path. Meta hasn't published a formal connector spec.