The MCP server reported nothing about its own usage, so the only signal for "is anyone running this?" was npm download counts — which conflate CI, mirrors and repeat installs, and say nothing about whether the server ever started or whether the devtools transport connected.

Instruments it with @posthog/mcp, reporting server start, tool calls, latency, errors, and which MCP client is driving it.

Privacy is enforced by an allowlist, not a denylist

The SDK captures tool arguments and responses unconditionally — there is no option to disable it (verified against 0.10.8 source: buildCapturedMcpParameters is called at three sites with no gate), and its built-in sanitizer only matches sensitive key names, so a field named flowContent would be transmitted verbatim. Devtools tool arguments carry player/plugin ids and invoke_action payloads, i.e. potentially customer flow data.

Every event is therefore filtered through an explicit set of known-safe property names, installed as a posthog-node client-level before_send — a chokepoint the SDK cannot route around, since we construct the PostHog client and it explicitly does not own one. A denylist would silently start leaking the first time a 0.x release added a new payload property; the allowlist drops unknown keys by default.

The SDK's context option is disabled. It defaults to ON and would inject a required context parameter into every tool schema, mutating our public API to ask the calling agent to narrate user intent in prose.

Identity

A random UUID at ~/.player-ui-devtools/install.json — deliberately not beside the flipper refcount in the OS temp dir, which is periodically reaped and would turn "unique installs" into "unique boots". When the home directory is unwritable the id is null and telemetry is skipped, rather than minting a per-run id that would inflate counts.

Toolchain

@posthog/mcp requires Node ^20.20.0 || >=22.22.0, which excludes the previous 22.15.1 pin. rules_nodejs is bumped 6.4.0 → 6.7.5 because 6.4.0 knows no Node newer than 22.15.1.

Also replaces the stale hardcoded server version "0.0.1" with the stamped __VERSION__, and flushes buffered events in stop() before bin/run calls process.exit(0).

Verification

42 tests across 7 files; //devtools/mcp:all (eslint + typecheck + vitest) all PASSED. The redaction suite asserts on the serialized payload — so a nested leak fails the test — and includes a case proving an unknown future property ($mcp_raw_request) is dropped.

Not yet done: the PostHog project key is still a placeholder, so telemetry is inert until one is provisioned. Once it is, verify redaction against a local listener before real use.

Release Notes

The MCP server now reports anonymous usage analytics — server starts, tool names, latency, and errors — so we can see how widely devtools is used and whether it works in the field.

Tool arguments and tool responses are never transmitted. Outgoing events are filtered through an allowlist of known-safe properties, so flow content cannot leave your machine.

Identity is a random UUID stored at ~/.player-ui-devtools/install.json; delete the file to reset it. Opt out with PLAYER_DEVTOOLS_TELEMETRY_DISABLED=1 or the cross-vendor DO_NOT_TRACK=1.

Breaking: @player-devtools/mcp now requires Node ^20.20.0 || >=22.22.0.