Limits & Current Scope

Everything here describes the current MCP surface. None of it is a statement about what Mailhub as a product can do. A capability existing elsewhere in Mailhub does not mean it exists here.

Protocol and client boundaries

• The server speaks Streamable HTTP.
• MCP is a user-scoped assistant surface, not the account-level Mailhub API.
• There are no MCP resources today, and no MCP prompts today. The eight tools are the entire surface.
• Mailhub does not implement dynamic client registration. A client cannot register itself; only a client Mailhub registered in advance can connect.
• Being MCP-compatible is not by itself enough. A client that speaks the protocol correctly still cannot connect without that registration, and the published server URL does not change that. Confirm supported clients and environments with Mailhub rather than inferring support.

Account and operation boundaries

• Parent account only. MCP provides no sub-account selection or switching mechanism, so an assistant sees the parent account's view rather than whichever sub-account a person may be working in on the web. Sub-account workflows are part of the Mailhub API surface, not of MCP today — see Work with sub-accounts.
• Listing is pagination only. mailhub_list_orders takes a page and a page size, and exposes no search, status filter, carrier filter, date range, or sort control, even where the Mailhub application offers them.
• Draft Orders are not listed, and are outside the normal MCP read surface.
• Each changing tool acts on one Order, Shipment, or Label at a time. There is no bulk-action tool.
• After creation, MCP exposes status changes rather than general-purpose Order editing. There is no tool for editing an existing Order's addresses or parcel data.
• Order detail has to resolve. mailhub_get_order returns the first Shipment Mailhub can resolve, and answers MCP_ORDER_DETAILS_UNAVAILABLE when it cannot resolve one.
• There is no dedicated Label-purchase status polling tool. A purchase can return while the Label is still being generated — see Working with Labels.
• A Label comes back as a link, not as bytes. The file is downloaded from the Mailhub application after opening the link; it never enters the conversation.

What MCP does not manage

Not available through MCP today	Where it belongs
Managing Mailhub users	The Mailhub application
Turning Agent Access on or off	The Mailhub application, by an authorized account user
Changing the agent spend limit	The Mailhub application, by an authorized account user
Carrier account setup and credentials	The Mailhub application
Adding funds to the wallet	The Mailhub application
Pickup scheduling	Outside the current MCP surface
Customs and document workflows	Outside the current MCP surface
Batch and bulk operations	Outside the current MCP surface

An assistant cannot widen its own limits

An assistant cannot grant itself Agent Access, and it cannot raise its own spend limit or add funds to the wallet. A purchase blocked by funds or by the limit is resolved outside MCP, by a person — see Confirmations & Spend Safety.

MCP does request Rates from the carriers already available to the account, and buys Labels against those Rates — it just does not configure them.

What to use instead

Need	Where to go
Unattended system-to-system integration	The Mailhub API
Working across sub-accounts	Work with sub-accounts
Carrier setup, wallet funding, account and user administration	The Mailhub application
Exact behavior of one tool	Tool Reference
Session lifetimes, confirmation, spend and retry rules	Authentication and Confirmations & Spend Safety
A failure you cannot place	Errors & Troubleshooting
The trust boundaries, for a review	Security Model
Anything this section does not answer	Developer Support