Technical finding

Privacy-safe OTel cannot identify the MCP server

The tested privacy-safe OpenTelemetry configuration redacted both official and custom MCP identity to custom. That makes it useful for aggregate counters, but not trustworthy as the source of truth for MCP, skill, or plugin identity.

See the local source of truth Understand the category

Observed

Official and custom MCP identity both became custom.

Consequence

Two different servers can no longer be distinguished from that field.

Decision

OTel is not the identity source of truth.

The experiment

A privacy property removed the dimension the product needed

KeepRails needs to attribute evidence to a concrete configured asset. A counter without a defensible identity cannot answer which server was present or used.

What OTel could still tell us

Aggregate counters remain usable under the tested configuration. They can contribute a total without pretending to identify the asset behind it.

What OTel could not tell us

It could not preserve the MCP identity needed to distinguish official and custom servers. Treating custom as a server name would manufacture certainty.

The implementation decision

Configuration is the source of identity

The local audit available today establishes identity from local configuration inventory. It does not need telemetry to say what is installed, where it is defined, or which permissions it declares.

Inventory locally

Resolve MCP servers, skills, plugins, scope, provenance, version, transport, and declared permissions from configuration on the machine.

Keep observation local

When observation is enabled in a later product phase, the design keeps transcript parsing on the device and reduces it to approved identifiers and counters.

Label missing attribution

Evidence that cannot be defensibly matched remains unattributable. It is counted, not hidden and not assigned to a convenient asset.

Scope

This is not an argument against OpenTelemetry

It is a narrower engineering result: under the tested privacy-safe configuration, OTel can carry aggregate counters but cannot be trusted for MCP identity. KeepRails uses the signal only for claims the signal can support.