Agentomy MCP Gateway

Governs any stdio MCP server by sitting between the agent and the server. Every tools/call is checked against your policy before it reaches the server. A refusal is answered by the gateway and never forwarded, so the side effect does not happen.

Nothing about the upstream server changes. It is not patched, not forked, and never learns it is being governed.

Why interpose instead of observe

A sidecar that watches MCP traffic and reports on it produces a record of the things it failed to stop. Sitting on the wire is what turns a report into a refusal.

Related MCP server: jamjet-policy

Install and run

# Instead of launching the MCP server directly:
#   my-mcp-server --flag
# launch it through the gateway:
AGENTOMY_ENDPOINT=https://your-agentomy \
AGENTOMY_API_KEY=... \
  agentomy-mcp-gateway -- my-mcp-server --flag

In an agent's MCP configuration, replace the server's command and args:

{
  "mcpServers": {
    "dev-tools": {
      "command": "agentomy-mcp-gateway",
      "args": ["--", "the-original-command", "--its", "--flags"],
      "env": { "AGENTOMY_ENDPOINT": "https://your-agentomy", "AGENTOMY_API_KEY": "..." }
    }
  }
}

That is the whole integration. One config change, per agent, by the operator.

What it does to the protocol

Requests are adjudicated in arrival order. Deciding concurrently would let a later call reach the server before an earlier one was resolved, which is a reordering bug that only shows up under load.

Fail-closed, and what that costs you

Every failure path denies:

The honest trade: if the platform is down, governed tools stop working. That is the correct behaviour for a governance component and it is a real availability coupling. Run the platform accordingly.

The reasons are distinct on purpose. An operator seeing governance_unreachable has an outage; one seeing policy_denied has a policy question. Collapsing them into "denied" would make the two indistinguishable at exactly the moment the difference matters.

A missing authorized field denies rather than being read for truthiness, because a truthiness check turns any unexpected payload, including an error object, into an allow.

What it does not do

It governs actions, not discovery. tools/list passes through. Narrowing what an agent may see while leaving what it may do ungoverned would be theatre in the wrong place.

It does not rewrite results. The gateway adjudicates requests; making it edit responses would turn it into a participant in the conversation rather than a gate on it.

It does not inspect arguments semantically. Policy receives the tool name and the argument keys, not the values. Argument-level policy is a platform concern and sending full argument values to a decision endpoint would put file contents and shell commands into a second system.

Licence

Apache-2.0.