Transports

fast-classifier speaks two transports to Fastmail behind one MailProvider interface. Pick with -p jmap / -p mcp on the CLI or provider.type in config.

	JMAP (default)	MCP
Token env var	FASTMAIL_API_TOKEN	FASTMAIL_MCP_TOKEN
Endpoint	api.fastmail.com/jmap/session	api.fastmail.com/mcp (official)
Page size	100	50 — server hard cap
Keep-list negation	full server-side NOT filter	-from: literal addresses only; re-checked client-side
Label creation	explicit Mailbox/set (nested paths, modal parent)	no create tool — addLabels auto-creates missing labels
Search totals	real totals (calculateTotal)	none (position-only paging)

Distinct credentials

The tokens are distinct credentials — a JMAP API token does not work against the MCP endpoint and vice versa. Both come from Fastmail under Settings → Privacy & Security → Integrations → API tokens; see the Quickstart.

The transport differences are handled automatically — the page-size caps, keep-list re-checks, and label-creation strategies are all encoded in the providers. The full list of server behaviors each transport encodes is in the Fastmail API quirks appendix, and the transport internals are documented as core concepts: the MCP handshake and the JMAP client.