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The MCP Inspector provides comprehensive RPC logging capabilities that allow you to monitor all JSON-RPC messages exchanged between the inspector and your MCP servers in real-time. This feature is essential for debugging, understanding server behavior, and troubleshooting connection issues.

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Overview

Detailed view of an expanded RPC message with JSON payload

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What is RPC Logging?

RPC (Remote Procedure Call) logging captures every JSON-RPC message sent to and received from MCP servers. This includes:
  • Tool calls: Requests to execute tools and their responses
  • Resource requests: Queries for resources and their results
  • Prompt requests: Prompt execution requests and responses
  • Notifications: Server-initiated notifications
  • Errors: Error responses and connection issues

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Opening the RPC Panel

1

Navigate to a Tab

Open the Tools, Resources, or Prompts tab for a connected server.
2

Locate RPC Panel

The RPC Messages panel appears at the bottom of the left sidebar. It starts collapsed by default.
3

Expand Panel

Click on the “RPC Messages” header to expand the panel. You can resize it by dragging the handle above it.
RPC logging interface showing message list

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Understanding the Interface

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Message List

Each RPC message is displayed as a row with:
  • Timestamp: Local time when the message was received
  • Direction Badge:
    • ↑ SEND - Outgoing messages from inspector to server
    • ↓ RECEIVE - Incoming messages from server to inspector
  • Method Name: The JSON-RPC method being called (e.g., tools/call, resources/read)
  • Expandable Content: Click to view the full JSON payload

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Technical Details

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Message Format

Each logged message contains: 
{
  id: string;              // Unique message ID
  serverId: string;        // Server identifier
  direction: "SEND" | "RECEIVE";
  method: string;          // JSON-RPC method name
  timestamp: string;       // ISO timestamp
  payload: unknown;        // Full JSON-RPC payload
}