Capability matrix

What a connected client can rely on, generated from the same catalog that registers the server. Counts include the gated families (exec and notify), which register only when their gates open.

Capability	What arrowhead serves
Tools	38 across 10 families, every one with structured output, behavior annotations, and a required OAuth scope
Resources	2 static resources and 1 resource template, including the arrowhead://integrity surface digest
Prompts	2, each scope-guarded like a tool
Argument completions	Served for prompt and template arguments, rate-limited per caller
Elicitation	Destructive document writes confirm through the client when it supports elicitation; an explicit flag stands in when it cannot
Cache hints	List results and resource reads carry private-scope TTLs in _meta
Protocol eras	One endpoint serves the sessionless 2026-07-28 protocol and handshake-era clients that send initialize
Transports	stdio for local pipes and streamable HTTP for deployments
Authorization	OAuth 2.1 resource server (RFC 9728 discovery), scopes split by verb, plus a default-deny per-resource policy engine
Tasks	Handle-based asynchronous scans and timer schedules, owner-scoped

Profiles select families; the tool reference carries the per-family breakdown and the configuration reference every gate and ceiling. Not implemented, by design or not yet: sampling, resource subscriptions, list pagination, and progress notifications are optional protocol features a catalog of this size does not need.