Composition axis
The seven roles a server can play.
Category tells you what a server connects to. Role tells you whether it expects to work alongside anything else. It is an editorial classification of position, not a judgment of quality. No role makes a server better than another.
Source
Provides data. A read-only feed from one provider; it answers questions, doesn't act, and doesn't expect other servers alongside it.
Example · Morningstar
Source servers →System
Provides one system's data and actions. Reads and writes inside a single product of record; it can act, but only within its own walls.
Example · Salesforce
System servers →Gateway
Reaches many systems at once. One connection that fans out to hundreds of apps, trading depth for breadth.
Example · Zapier
Gateway servers →Aggregator
Normalizes several systems behind one interface. Hides many underlying providers behind a single normalized shape.
Example · Truthifi
Aggregator servers →Directory
Helps you find capabilities. Doesn't hold the data itself. It points you to the servers that do.
Example · WealthMCP
Directory servers →Domain
Specialized public intelligence. Turns a public dataset into a queryable, agent-ready domain expert.
Example · ADVmcp, 5500mcp
Domain servers →Composition
Combines other servers' capabilities to reach an outcome. Orchestrates data and domain servers into a finished decision, not just a data point.
Example · ValuationMCP
Composition servers →
Roles are assigned editorially and can be filtered on the directory. A listing shows its role as a badge; hovering it repeats the one-liner above. Listings are informational only. Always verify a server with its publisher before connecting it to client data.
Filter the directory by role →