MCP Error
Industry Definition Set • Entity Resolution Path: /glossary/mcp-error
Quick Answer / TL;DR
The error payload in a JSON-RPC response message, containing a code, message, and optional data when a request fails.
Key Takeaways
- Failure response payload in JSON-RPC.
- Contains code, message, and optional data.
- Standard codes defined by the JSON-RPC spec.
- Custom codes can be defined for domain-specific errors.
Definitive Statement: The error payload in a JSON-RPC response message, containing a code, message, and optional data when a request fails.
Technical Context & Protocol Usage
- Detailed Explanation
- When a JSON-RPC request fails, the response contains an `error` object with a numeric `code`, a string `message`, and optional `data`. Standard codes include `-32700` (parse error), `-32600` (invalid request), `-32601` (method not found), and `-32603` (internal error). Servers can also define custom codes for domain-specific errors.
Format & Payload Metadata
Format: JSON object per JSON-RPC 2.0
Latency: No overhead; error serialization
Real-World Implementation Use Case
A client calls a tool that does not exist; the server responds with error code `-32601` (method not found).
Cite This Page
MLA Style:
MCPserver.in Engineering. "MCP Error." MCPserver.in Knowledge Hub, 20 July 2026, mcpserver.in/glossary/mcp-error.
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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