Execution Boundaries for MCP

scv-triage-runtime is the Python package that powers this demo. It is a deterministic, trusted-local, non-production, non-live simulation whose three read-only MCP tools return bounded policy verdicts, never live infrastructure state.

Architecture

graph TB
    DB[("Shared demo.sqlite3")]

    subgraph boundary["Execution-Boundary MCP Server"]
        direction TB
        R1["MCP request"] --> RT["Runtime<br/>request validation"]
        RT -->|"valid request"| PV["SQLite Provider"]
        RT -->|"invalid request"| FC["Bounded Result<br/>INDETERMINATE"]
        PV -.->|"read-only query"| DB
        PV -->|"raw evidence"| EB["Semantic Evidence Boundary<br/>7 validation layers"]
        PV -->|"provider failure"| FC
        EB -->|"accepted"| NE["Immutable normalized evidence"]
        EB -->|"rejected"| FC
        NE --> PL["Policy<br/>deterministic verdict"]
        PL --> OUT["Bounded Result<br/>outcome + findings + actions"]
    end

    subgraph thin["Thin-Wrapper MCP Server"]
        direction TB
        R2["MCP request"] --> SQL["Source-specific SQL query"]
        SQL -.->|"read-only query"| DB
        SQL --> RAW["Measurement rows<br/>no verdict, no policy"]
    end

The semantic evidence boundary is not a pass-through. It independently validates seven layers, then emits immutable normalized evidence for policy evaluation:

SemanticEvidenceBoundary
├── envelope identity            schema, tool, profile match the request
├── request identity             hostname, at, frm, to match the request
├── coverage                     the point or window is inside packaged coverage
├── temporal binding             evidence timestamps fall within the request window
├── scope                        host and fleet scope match the requested target
├── row shape and bounds         source, fields, types, and numeric ranges are valid
├── ordering / uniqueness / cap  no duplicate keys, monotonic order, fixed cap
└── output guarantee             immutable normalized evidence

Public MCP tools:

• triage_server(hostname, at?)

• fleet_health(at?)

• investigate_timeline(hostname, frm, to)

Every result is a simulation snapshot. Lead a point result with its evaluation timestamp; lead a timeline result with its half-open [frm, to) range. Timeline results do not establish an exact state-transition time or root cause.

severity is categorical policy metadata, not a calculation of duration, impact, or confidence. Under the policy, SERVER_OFFLINE maps to HIGH. HEALTHY is not a reservation-availability claim. NO_DATA is a valid empty result; INDETERMINATE means required evidence cannot be reliably evaluated. actions require approval and are non-executable.

Why evidence was rejected

For INDETERMINATE, findings.kind names the bounded validation class that stopped evaluation:

A thin provider pass-through may relay data or structured errors, but it does not independently validate request identity, host scope, time/window, order, uniqueness, caps, and payload bounds. The normalized semantic evidence boundary does, and returns one bounded rejection class without backend disclosure when those invariants do not support a trustworthy verdict. These fixed categories are rejection classes, not exhaustive root causes. They never expose SQL, paths, database/provider identities, raw exception text, or rejected values. Their severity is always HIGH because no trustworthy verdict can be produced—not because incident impact is high. Synthetic failures retain schema-v1 evidence state defective; normal states remain COMPLETE, EMPTY, and NOT_APPLICABLE. Required missing (and an empty fleet) takes precedence over required stale.

Related MCP server: tracegraph

Getting started

Prerequisites

• Python 3.12 or later

• SQLite 3.37 or later (pre-installed on macOS and most Linux)

• pipx

If your system Python is older than 3.12, install 3.12 first. On Linux without sudo, use uv:

curl -LsSf https://astral.sh/uv/install.sh | sh
uv python install 3.12

If pipx is not installed:

curl -sSf https://pipx.pypa.dev/install.py | python3

Install

If your system Python is 3.12+, install directly:

pipx install git+https://github.com/kc-ml2/mcp-execution-boundaries.git

If pipx defaults to an older Python, specify 3.12 explicitly:

pipx install --python 3.12 git+https://github.com/kc-ml2/mcp-execution-boundaries.git

This puts scv-triage-stdio on your PATH. Most MCP clients find it directly. If yours doesn't, run command -v scv-triage-stdio and paste the output as the command value.

Configure an MCP client

Claude Desktop — edit claude_desktop_config.json:

{
  "mcpServers": {
    "scv-triage": {
      "command": "scv-triage-stdio",
      "args": [],
      "env": {
        "SCV_RUNTIME_ENVIRONMENT": "demo",
        "SCV_DEMO_PROFILE": "INCIDENT"
      }
    }
  }
}

Cursor — see deploy/cursor-mcp.example.json.

Restart and verify

Completely quit and reopen the MCP client. The server is ready when these three tools appear:

• triage_server

• fleet_health

• investigate_timeline

Switch profiles

At the INCIDENT evaluation point, triage_server(server-01) reports both STORAGE_CRITICAL_ENTRY (CRITICAL) and VIOLATION_PERIOD (HIGH). Co-present findings do not establish causation.

Change SCV_DEMO_PROFILE and restart the client.

Verify in the MCP client

After restarting, the client should list exactly three tools: triage_server, fleet_health, and investigate_timeline. If the server doesn't appear, run command -v scv-triage-stdio and use the printed absolute path as the command value instead.

Update

pipx upgrade scv-triage-runtime

Uninstall

pipx uninstall scv-triage-runtime

Install from source

git clone https://github.com/kc-ml2/mcp-execution-boundaries.git
cd mcp-execution-boundaries
python3.12 -m venv .venv
.venv/bin/pip install .

For this method, set command to the absolute <repo>/.venv/bin/scv-triage-stdio path.

Runtime gate

The server starts only when SCV_RUNTIME_ENVIRONMENT=demo and SCV_DEMO_PROFILE is exactly INCIDENT or CLEAR. Missing, production, or unsupported values abort before MCP protocol startup with no fallback.

License

MIT — see LICENSE.

Presentation

Presented at MCP Seoul 2026. See output/ for a structured output comparison between the execution-boundary server and a thin API wrapper on the same query.