Anyone who wants to know which MCP servers are running in their organization currently has to dig through agent configuration files. Dozens of files across repositories and developer laptops describe which agent may reach which server and which tools it finds there. Taken together, those files are the company’s MCP registry, just without search, access control, or an audit trail.
An MCP registry bundles this scattered information into a managed directory. It inventories every MCP server in an organization, governs access to their tools, and logs which agent calls what. This article explains why that building block becomes indispensable the moment agents reach production systems, and how an MCP registry differs from an MCP gateway and from public server directories.
An MCP registry is the central directory of all MCP servers in an organization. It inventories the servers along with their tools, uses roles to control which agent and which user may use which tool, and keeps a tamper-evident log of every access. Unlike an MCP gateway, which forwards tool calls at runtime, an MCP registry operates at the governance level. It answers what exists, who owns it, and who may use it.
Why the question comes up right now
Over the past twelve months, many teams have moved their first agents into production workflows. Each new use case brought MCP servers with it. Custom servers for internal APIs, ready-made servers for GitHub, Jira, or databases, plus experiments by individual developers. An inventory of ten or more servers builds up this way faster than most people expect.
In the API world, a human safety net compensates for a lot. A developer who is missing a piece of information will ask a colleague when in doubt, and will notice when something seems off. An agent lacks that corrective. It works with whatever its configuration offers, and it does so with every permission the stored token grants. An outdated or overly generous configuration therefore often goes unnoticed until an agent modifies production data it should only have read.
There’s a striking asymmetry here. For APIs, most organizations maintain catalogs, review processes, and audit trails. For the MCP servers through which agents access those same APIs, many places don’t even have a complete list.
What an MCP registry is and what it is not
An MCP registry is the inventory and governance layer for MCP servers. It lists every server with its endpoint, transport, and authentication, along with its tools, makes that inventory searchable, and defines who may use what. The term, however, is currently used for three different things, which muddies the picture.
- An internal MCP registry inventories and governs the servers of one organization. That is the form this article is about.
- An MCP gateway sits between agent and server at runtime. It forwards tool calls, handles authentication and rate limiting, and therefore belongs to the runtime infrastructure.
- Public directories such as Glama, PulseMCP, or Smithery list freely available servers from the wider ecosystem. They help you find ready-made building blocks, but they say nothing about what runs or what is allowed inside your own company.
The most important distinction concerns the gateway. An MCP registry is not a runtime proxy but design-time governance. It therefore has to work even when tool calls go straight from agent to server, and it stays neutral when several gateways are in play.
The four pillars of an MCP registry
Four capabilities turn a directory into a registry. Each of them answers a question that routinely stays open without one.
The catalog answers which servers exist and which tools they offer. Without it, teams build servers twice or wire up outdated endpoints, simply because nobody knows the inventory.
Access control answers who may use a tool. Without it, every agent inherits the full rights of its token, and an assistant meant for documentation questions can suddenly create production tickets.
The audit trail answers who actually used a tool. By the security review at the latest, that question becomes binding, and without a log all that remains is the tedious reconstruction from the logs of distributed systems.
Policies, finally, make rules enforceable, for instance that production tools stay locked for experimental agents. In most organizations this pillar comes last, because it builds on the other three.
The tool level is the real permission level
Anyone who governs access to MCP servers starts out thinking in servers. That granularity is deceptive, though. A single server frequently exposes dozens of tools, and between a read-only status tool and a destructive delete tool lies the entire risk surface of a system.
An MCP registry therefore has to model permissions per tool. In practice, allowlisting has proven itself. Whatever has been explicitly approved is available, and everything else stays locked. That reverses the burden of proof and prevents new tools of an updated server from becoming usable unnoticed.
The permission unit of an MCP registry is the individual tool, not the entire server. A server with thirty tools requires thirty separate approval decisions.
Start allowlisting with the writing tools. Read-only tools are usually uncritical. Writing tools deserve a deliberate approval per agent.
Where the registry gets its truth
A directory maintained by hand inevitably trails the changes. With MCP servers this gets worse, because a server’s tool list can change with every deployment. The reliable source is therefore the server itself.
The Model Context Protocol provides the foundation out of the box. Every MCP server answers the tools/list request with a machine-readable description of its tools and their parameters.
{
"tools": [
{
"name": "search_api_schemas",
"description": "Search schema definitions across all registered APIs",
"inputSchema": {
"type": "object",
"properties": { "query": { "type": "string" } }
}
}
]
}A registry that polls this response regularly and compares it against the last known state detects new, changed, and removed tools automatically. The mechanism mirrors the Git sync of an API catalog, except that the source here is the running server. Why automated reconciliation beats central curation so clearly is something we described for API catalogs in large organizations.
Registry and API catalog belong together
The closeness of the two disciplines is no coincidence. In most cases, MCP servers expose APIs that are already documented and cataloged, often generated straight from the OpenAPI spec. An organization that runs a well-maintained API catalog already owns half the registry. Ownership, lifecycle status, and consumer relationships are captured, and all that’s missing is the connection to the MCP layer.
In one engagement, a team ran three agents with overlapping MCP configurations. Asked which of them was allowed to write to the production ticket system, we got three different answers and not one that could be substantiated. The gap only surfaced in the security review, fortunately before the first incident.
For regulated industries, there’s a second connection. When agents access account or patient data, the same requirements apply as to any other processing, from the audit trail through data residency to running in your own infrastructure. A bank that has already established its API governance will subject MCP access to the same rules, and needs a registry that handles EU hosting and on-premise operation.
How api-portal.io supports this
api-portal.io takes the registry building blocks from the API world and brings them together for MCP. The API Catalog inventories MCP servers as first-class entries along with their tool lists. Roles and business groups control access down to the individual tool, and the audit trail logs changes as well as access. The built-in MCP Server additionally exposes the portal’s API knowledge itself as tools for Claude, GPT, and LangChain, secured via OAuth2 and isolated per tenant.
API Portal catalogs, secures, and audits MCP access to your API portfolio today. Try the built-in MCP Server for 14 days with your own specs.