exploring-mcp-tool-usage
Exploring MCP tool usage
Any MCP server instrumented with the @posthog/mcp SDK emits a $mcp_tool_call
event every time an agent invokes a tool. This skill is the front door for a
user who knows they want to look at their MCP tool usage but hasn't picked a
specific question. Offer the menu below, then route to the tool — or the focused
skill — that answers what they choose.
Governed metric first
When the question asks for an MCP failure rate or percentage, call posthog:metric-list before any typed tool or SQL recipe and look for mcp_tool_call_fail_pct. Run an approved, non-drifted match with posthog:data-catalog-metric-run for the canonical headline. If the user also asks which tool or harness drives failures, answer the headline first, then use the per-tool workflows below for a noncanonical breakdown. If no governed metric matches, say so and label the derived rate noncanonical.
Every per-tool tool here is gated behind the mcp-analytics flag, takes a
toolName (the effective tool name — resolved server-side, so pass the name the
agent actually invokes — except posthog:query-mcp-tool-failures, which
matches $exception events and so takes the raw registered $mcp_tool_name)
plus a dateRange, and runs the same query runner the tool-detail UI uses. So
results match the UI, and you never hand-write the HogQL.