Device capabilities

RouterOS is not one platform. The wireless stack, container support, PoE and several optional packages differ per device — and a tool that needs one of them normally discovers its absence the hard way, by running and getting back no such command. The model then sees a confusing parser error, often invents a fix, and burns two more calls.

The capability probe learns those facts once per device and uses them to answer before the round-trip.

What is probedCopy Anchor Link

One batch of read-only commands, on first use, cached for six hours:

Every probe is individually optional. /system device-mode does not exist before RouterOS 7.13 and /system routerboard does not exist on CHR — an absent menu records absence rather than failing the probe.

A disabled package is not counted as present. RouterOS lists a package flagged X as installed, but it cannot serve its menu.

Seeing itCopy Anchor Link

get_device_capabilities        # version, board, stack, packages, device-mode
refresh_device_capabilities    # force a reprobe, bypassing the 6h cache

Reach for get_device_capabilities when a tool reported "not available on this device" and you want to know exactly what is missing. Reach for refresh_device_capabilities after installing a package, upgrading firmware, or changing device-mode.

How it gatesCopy Anchor Link

A tool may declare what it needs:

requires: { packages: ["container"], deviceMode: "container", minVersion: "7.0" }
requires: { routerBoard: true }
requires: { wirelessStack: "wifi" }
requires: { board: /^CRS3/ }

Two things then happen.

At call time — the guard. An unsupported invocation returns a sentence naming what is missing, instead of a RouterOS parser error, and the handler never runs. This always applies, regardless of the setting below.

At listing time — annotation. The tool's description gains a prefix like [unavailable on this device: needs the container package installed and enabled], which is what the model reads when choosing a tool.

Only three modules currently declare requirements — container, User Manager and PoE — because those are unambiguous: a missing package or absent PoE hardware cannot be worked around. The wireless modules deliberately do not, since they already probe each command path per call and work across all three stacks; gating them would remove working behaviour to gain a label.

capabilityGatingCopy Anchor Link

mikrotik-mcp serve --capability-gating=off
MIKROTIK_MCP__CAPABILITY_GATING=filter mikrotik-mcp serve

filter is honoured only with a single device. With several routers the tool list is global while capabilities are per-device, so hiding a tool unsupported on one would remove it for every other one; multi-device setups fall back to annotate and log a warning.

Two things worth knowingCopy Anchor Link

An unknown capability never blocks. If the probe could not determine something — the device was unreachable, or answered none of the commands — every predicate passes and the tool runs. Refusing to act because a probe came back empty would be a worse failure than letting RouterOS answer for itself. The probe is an optimisation, not an authority.

Annotation needs a probe that already resolved. MCP tool descriptions are registered once when the server starts and cannot wait for I/O, so a cold cache means every tool lists normally. In practice annotate and filter take effect on the next server start after a probe exists, while the call-time guard works from the very first call. That asymmetry is inherent to MCP's static tool list — the alternative, probing every device before registering anything, would add a network round-trip to startup and fail closed on an unreachable router.

CacheCopy Anchor Link

In-memory, six hours, keyed per device. Concurrent callers share one in-flight probe rather than each firing their own. It is dropped automatically on a config reload and after a firmware upgrade, and manually by refresh_device_capabilities.

Nothing is persisted: a restart costs one probe per device, which is cheaper than reasoning about a stale model after an upgrade.