Implementation:BerriAI Litellm MCP Types

Attribute	Value
Sources	litellm/types/mcp.py
Domains	MCP (Model Context Protocol), Tool Calling, Server Configuration, Authentication
Last Updated	2026-02-15 16:00 GMT

Overview

Type definitions for the Model Context Protocol (MCP) subsystem, covering server configuration, transport protocols, authentication, credential management, cost tracking, and pre/during/post call hook request/response objects.

Description

This module defines the complete type hierarchy for LiteLLM's MCP integration. MCP enables LLMs to interact with external tools hosted on MCP servers. The types cover:

• Protocol enums -- MCPTransport (sse, http, stdio), MCPSpecVersion (2024-11-05, 2025-03-26, 2025-06-18), MCPAuth (none, api_key, bearer_token, basic, authorization, oauth2).
• Server configuration -- MCPPublicServer for safe public server params, MCPStdioConfig for local stdio-based servers.
• Credentials and cost -- MCPCredentials for authentication values including OAuth2 support, MCPServerCostInfo for per-query and per-tool cost tracking.
• Hook objects -- Pydantic models for the three MCP guardrail hook phases:
  • MCPPreCallRequestObject / MCPPreCallResponseObject -- Before tool execution; can modify arguments or block the call.
  • MCPDuringCallRequestObject / MCPDuringCallResponseObject -- During tool execution; can cancel ongoing calls.
  • MCPPostCallResponseObject -- After tool execution; wraps the MCP response content.

Usage

Import from this module when:

• Configuring MCP servers in the LiteLLM proxy YAML configuration.
• Implementing custom MCP guardrail hooks (pre_mcp_call, during_mcp_call).
• Working with MCP tool call cost tracking.
• Building stdio-based MCP server integrations.

Code Reference

Source Location

litellm/types/mcp.py (177 lines)

Key Types

Type Name	Kind	Description
MCPTransport	str, Enum	Transport protocols: sse, http, stdio
MCPSpecVersion	str, Enum	MCP spec versions: 2024-11-05, 2025-03-26, 2025-06-18
MCPAuth	str, Enum	Authentication methods: none, api_key, bearer_token, basic, authorization, oauth2
MCPTransportType	Literal	Literal type alias for MCPTransport values
MCPSpecVersionType	Literal	Literal type alias for MCPSpecVersion values
MCPAuthType	Optional[Literal]	Optional literal type alias for MCPAuth values
MCPPublicServer	BaseModel	Public MCP server metadata (server_id, name, url, transport, auth_type)
MCPCredentials	TypedDict	Auth credentials (auth_value, client_id, client_secret, scopes)
MCPServerCostInfo	TypedDict	Cost tracking (default_cost_per_query, tool_name_to_cost_per_query)
MCPStdioConfig	TypedDict	Stdio server config (command, args, env)
MCPPreCallRequestObject	BaseModel	Pre-call hook input (tool_name, arguments, server_name, user_api_key_auth)
MCPPreCallResponseObject	BaseModel	Pre-call hook output (should_proceed, modified_arguments, error_message)
MCPDuringCallRequestObject	BaseModel	During-call hook input (tool_name, arguments, server_name, start_time)
MCPDuringCallResponseObject	BaseModel	During-call hook output (should_continue, error_message)
MCPPostCallResponseObject	BaseModel	Post-call hook output wrapping MCP response content

Import

from litellm.types.mcp import (
    MCPTransport,
    MCPSpecVersion,
    MCPAuth,
    MCPPublicServer,
    MCPCredentials,
    MCPServerCostInfo,
    MCPStdioConfig,
    MCPPreCallRequestObject,
    MCPPreCallResponseObject,
    MCPDuringCallRequestObject,
    MCPDuringCallResponseObject,
    MCPPostCallResponseObject,
)

I/O Contract

MCPPublicServer

Field	Type	Default	Description
server_id	str	(required)	Unique server identifier
name	str	(required)	Display name
alias	Optional[str]	None	Optional alias
server_name	Optional[str]	None	Optional server name
url	Optional[str]	None	Server URL
transport	MCPTransportType	(required)	Transport protocol (sse, http, stdio)
spec_path	Optional[str]	None	Path to MCP spec file
auth_type	Optional[MCPAuthType]	None	Authentication type
mcp_info	Optional[Dict[str, Any]]	None	Additional MCP metadata

MCPPreCallRequestObject (Input)

Field	Type	Default	Description
tool_name	str	(required)	Name of the MCP tool being called
arguments	Dict[str, Any]	(required)	Arguments for the tool call
server_name	Optional[str]	None	MCP server hosting the tool
user_api_key_auth	Optional[Dict[str, Any]]	None	Authenticated user info
hidden_params	HiddenParams	HiddenParams()	Internal logging metadata

MCPPreCallResponseObject (Output)

Field	Type	Default	Description
should_proceed	bool	True	Whether to proceed with the tool call
modified_arguments	Optional[Dict[str, Any]]	None	Modified arguments (replaces original if set)
error_message	Optional[str]	None	Error message if should_proceed is False
hidden_params	HiddenParams	HiddenParams()	Internal logging metadata

MCPPostCallResponseObject (Output)

Field	Type	Description
mcp_tool_call_response	List[Union[MCPTextContent, MCPImageContent, MCPEmbeddedResource]]	The MCP tool call response content
hidden_params	HiddenParams	Internal logging metadata

Usage Examples

Configuring an MCP server

from litellm.types.mcp import MCPPublicServer, MCPTransport, MCPAuth

server = MCPPublicServer(
    server_id="my-tools",
    name="My Tool Server",
    url="https://tools.example.com/mcp",
    transport=MCPTransport.http,
    auth_type=MCPAuth.bearer_token,
)

Configuring a stdio MCP server

from litellm.types.mcp import MCPStdioConfig

stdio_config: MCPStdioConfig = {
    "command": "npx",
    "args": ["-y", "@modelcontextprotocol/server-filesystem", "/tmp/data"],
    "env": {"NODE_ENV": "production"},
}

MCP credentials with OAuth2

from litellm.types.mcp import MCPCredentials

creds: MCPCredentials = {
    "client_id": "my-client-id",
    "client_secret": "my-client-secret",
    "scopes": ["read", "write"],
}

Setting per-tool cost tracking

from litellm.types.mcp import MCPServerCostInfo

cost_info: MCPServerCostInfo = {
    "default_cost_per_query": 0.001,
    "tool_name_to_cost_per_query": {
        "web_search": 0.01,
        "code_interpreter": 0.05,
    },
}

Building a pre-call hook request

from litellm.types.mcp import MCPPreCallRequestObject

request = MCPPreCallRequestObject(
    tool_name="web_search",
    arguments={"query": "latest news"},
    server_name="my-tools",
)

Related Pages

• Guardrail Types -- Guardrail event hooks include pre_mcp_call and during_mcp_call that use these MCP types.
• Agent Types -- Agent types for A2A protocol that may invoke MCP tools.
• Service Types -- Service monitoring types that can track MCP server health.