[BUG] OpenTelemetry logs MCP tools as generic 'mcp_tool' instead of specific tool names like 'mcp__context7__resolve-library-id'

Summary

When MCP tools are called, OpenTelemetry telemetry logs them with tool_name: "mcp_tool" instead of the specific tool name following the mcp__<server>__<tool> pattern. This prevents building dashboards that show MCP usage broken down by server name (e.g., context7, notion, sentry).

Steps to Reproduce

1. Enable Claude Code telemetry with OTLP export to Loki:

``json
{
"env": {
"CLAUDE_CODE_ENABLE_TELEMETRY": "1",
"OTEL_METRICS_EXPORTER": "otlp",
"OTEL_LOGS_EXPORTER": "otlp",
"OTEL_EXPORTER_OTLP_ENDPOINT": "http://localhost:4317"
}
}
``

1. Configure MCP servers (e.g., context7, notion, sentry)

1. Make MCP tool calls in a Claude Code session

1. Query the telemetry logs:

``bash
curl -G 'http://localhost:3100/loki/api/v1/query_range' \
--data-urlencode 'query={service_name="claude-code"}' | \
jq '.data.result[] | select(.stream.tool_name == "mcp_tool") | .stream'
``

Expected Behavior

Based on the monitoring-usage documentation, tool_name should contain the full MCP tool name:

{
  "tool_name": "mcp__context7__resolve-library-id",
  "event_name": "tool_result",
  "success": "true"
}

This would allow grouping/filtering by MCP server name using regex like mcp__(?P<mcp_server>[^_]+)__.*.

Actual Behavior

All MCP tools are logged with a generic tool_name:

{
  "tool_name": "mcp_tool",
  "mcp_server_scope": "user",
  "event_name": "tool_result",
  "success": "true"
}

There is no field indicating which specific MCP server (context7, notion, sentry) was called.

Impact

Cannot build Grafana dashboards showing:

• Top MCP servers by call count
• MCP usage breakdown by server name
• Performance metrics per MCP server

Proposed Solution

Either:

1. Option A: Log the full tool name as mcp__<server>__<tool> in the tool_name field (matching documentation)
2. Option B: Add a separate mcp_server_name field to the telemetry attributes

Environment

• Claude Code version: 2.1.2
• OS: macOS (Darwin 24.6.0)
• MCP servers: context7, notion, sentry (all working correctly)

Evidence

Telemetry stream for an MCP call:

{
  "tool_name": "mcp_tool",
  "mcp_server_scope": "user",
  "event_name": "tool_result",
  "duration_ms": "1838",
  "success": "true",
  "session_id": "2dae27f9-d02e-43f9-99cb-4eb835457f09",
  "service_version": "2.1.2"
}

Compare to non-MCP tools which log correctly:

{
  "tool_name": "Bash",
  "event_name": "tool_result"
}

Related

• Hooks documentation shows MCP tools follow mcp__<server>__<tool> pattern
• Not related to #16371 (that issue is about tools not being registered; our MCP tools work fine)