MCP Request ID
Industry Definition Set • Entity Resolution Path: /glossary/mcp-request-id
Quick Answer / TL;DR
A unique identifier included in every JSON-RPC request message, used to match responses and support cancellation.
Key Takeaways
- Unique identifier per JSON-RPC request.
- Used to correlate requests with responses.
- Required for targeting requests for cancellation.
- Can be a number or string.
Definitive Statement: A unique identifier included in every JSON-RPC request message, used to match responses and support cancellation.
Technical Context & Protocol Usage
- Detailed Explanation
- Each JSON-RPC request carries an `id` field (a number or string). The server must include the same `id` in its response. This allows clients to correlate responses with outstanding requests, handle out-of-order responses, and target specific requests for cancellation.
Format & Payload Metadata
Format: JSON-RPC `id` field (number or string)
Latency: No overhead; metadata-only
Real-World Implementation Use Case
A client sends three concurrent tool calls with IDs 1, 2, and 3; it matches the server's responses back to the original calls by ID.
Cite This Page
MLA Style:
MCPserver.in Engineering. "MCP Request ID." MCPserver.in Knowledge Hub, 20 July 2026, mcpserver.in/glossary/mcp-request-id.
Related Terms
Model Context Protocol (MCP)
An open, secure protocol that standardizes how artificial intelligence agents and large language models (LLMs) exchange context, tools, prompts, and data resources with external servers.
JSON-RPC 2.0
A lightweight, stateless remote procedure call (RPC) protocol defined in JSON that utilizes request, response, and notification message frames.
Stdio Transport (Standard Input/Output)
A local-only transport mechanism where the AI client spawns the MCP server as a child process and communicates via standard input (stdin) and standard output (stdout) channels.
SSE Transport (Server-Sent Events)
A lightweight, unidirectional HTTP-based streaming protocol used by remote MCP servers to push messages to AI clients, with client-to-server writes sent over standard POST requests.
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