protocol

package
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 Go to latest Published: Mar 19, 2026 License: Apache-2.0 Imports: 3 Imported by: 0

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Overview

Copyright 2026 Teradata

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at 

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. Package protocol implements the Model Context Protocol (MCP) JSON-RPC 2.0 layer. This package provides types and utilities for MCP protocol communication.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at 

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. Package protocol implements MCP protocol types for the Model Context Protocol.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at 

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. Package protocol provides validation utilities for MCP protocol.

Index

Constants

View Source 
const (
	ParseError     = -32700 // Invalid JSON
	InvalidRequest = -32600 // Invalid JSON-RPC
	MethodNotFound = -32601 // Method doesn't exist
	InvalidParams  = -32602 // Invalid parameters
	InternalError  = -32603 // Internal error
	ServerError    = -32000 // Server-specific error (to -32099)
)

Standard JSON-RPC error codes

View Source 
const (
	// ExtensionID is the well-known extension identifier for MCP Apps (UI support)
	ExtensionID = "io.modelcontextprotocol/ui"

	// ResourceMIME is the MIME type for MCP App HTML resources
	ResourceMIME = "text/html;profile=mcp-app"

	// UIScheme is the URI scheme prefix for MCP App resources
	UIScheme = "ui://"
)

MCP Apps extension constants

View Source 
const JSONRPCVersion = "2.0"

JSONRPCVersion is the required version string for JSON-RPC 2.0

View Source 
const ProtocolVersion = "2024-11-05"

ProtocolVersion is the MCP protocol version supported by this implementation

Variables

This section is empty.

Functions

func ClientSupportsApps added in v1.2.0 

func ClientSupportsApps(extensions map[string]interface{}) bool

ClientSupportsApps checks whether a client's extensions indicate MCP Apps support. This is determined by the presence of the ExtensionID key in the extensions map.

func ServerAppsExtension added in v1.2.0 

func ServerAppsExtension() map[string]interface{}

ServerAppsExtension builds the extensions map a server should return to advertise MCP Apps support during initialization.

func SetUIToolMeta added in v1.2.0 

func SetUIToolMeta(tool *Tool, meta *UIToolMeta)

SetUIToolMeta attaches UI metadata to a Tool's _meta field. Initializes the Meta map if nil.

func ValidateRequest 

func ValidateRequest(req *Request) error

ValidateRequest validates a JSON-RPC request

func ValidateResponse 

func ValidateResponse(resp *Response) error

ValidateResponse validates a JSON-RPC response

func ValidateToolArguments 

func ValidateToolArguments(tool Tool, arguments map[string]interface{}) error

ValidateToolArguments validates tool arguments against JSON Schema

Types

type CallToolParams 

type CallToolParams struct {
	Name      string                 `json:"name"`
	Arguments map[string]interface{} `json:"arguments,omitempty"`
}

CallToolParams contains parameters for tools/call

type CallToolResult 

type CallToolResult struct {
	Content           []Content              `json:"content"`                     // Array of content items
	IsError           bool                   `json:"isError,omitempty"`           // Deprecated, use proper errors
	StructuredContent map[string]interface{} `json:"structuredContent,omitempty"` // Structured output (MCP 2025-03-26)
}

CallToolResult is the response from tools/call

type ClientCapabilities 

type ClientCapabilities struct {
	Roots    *RootsCapability    `json:"roots,omitempty"`
	Sampling *SamplingCapability `json:"sampling,omitempty"`
}

ClientCapabilities declares what the client supports

type Content 

type Content struct {
	Type     string       `json:"type"` // "text", "image", "resource"
	Text     string       `json:"text,omitempty"`
	Data     string       `json:"data,omitempty"`     // Base64 for images
	MimeType string       `json:"mimeType,omitempty"` // For images/resources
	Resource *ResourceRef `json:"resource,omitempty"` // For resource type
}

Content represents different types of content (text, image, resource)

type Error 

type Error struct {
	Code    int             `json:"code"`           // Error code
	Message string          `json:"message"`        // Human-readable message
	Data    json.RawMessage `json:"data,omitempty"` // Additional error info
}

Error represents a JSON-RPC 2.0 error

func NewError 

func NewError(code int, message string, data interface{}) *Error

NewError creates a standard JSON-RPC error

func (*Error) Error 

func (e *Error) Error() string

Implement error interface for Error

type GetPromptParams 

type GetPromptParams struct {
	Name      string                 `json:"name"`
	Arguments map[string]interface{} `json:"arguments,omitempty"`
}

GetPromptParams contains parameters for prompts/get

type GetPromptResult 

type GetPromptResult struct {
	Description string          `json:"description,omitempty"`
	Messages    []PromptMessage `json:"messages"`
}

GetPromptResult is the response from prompts/get

type Implementation 

type Implementation struct {
	Name    string `json:"name"`
	Version string `json:"version"`
}

Implementation describes client or server implementation details

type InitializeParams 

type InitializeParams struct {
	ProtocolVersion string                 `json:"protocolVersion"`
	Capabilities    ClientCapabilities     `json:"capabilities"`
	ClientInfo      Implementation         `json:"clientInfo"`
	Extensions      map[string]interface{} `json:"extensions,omitempty"`
}

InitializeParams contains parameters for the initialize request

type InitializeResult 

type InitializeResult struct {
	ProtocolVersion string                 `json:"protocolVersion"`
	Capabilities    ServerCapabilities     `json:"capabilities"`
	ServerInfo      Implementation         `json:"serverInfo"`
	Extensions      map[string]interface{} `json:"extensions,omitempty"`
}

InitializeResult contains the server's response to initialize

type LogNotification 

type LogNotification struct {
	Level  string      `json:"level"` // "debug", "info", "warning", "error"
	Logger string      `json:"logger,omitempty"`
	Data   interface{} `json:"data"`
}

LogNotification sends log messages from server to client

type LoggingCapability 

type LoggingCapability struct{}

type ModelHint 

type ModelHint struct {
	Name string `json:"name,omitempty"`
}

ModelHint suggests model preferences

type ModelPreferences 

type ModelPreferences struct {
	Hints                []ModelHint `json:"hints,omitempty"`
	CostPriority         *float64    `json:"costPriority,omitempty"`         // 0-1
	SpeedPriority        *float64    `json:"speedPriority,omitempty"`        // 0-1
	IntelligencePriority *float64    `json:"intelligencePriority,omitempty"` // 0-1
}

ModelPreferences specifies LLM selection preferences

type ProgressNotification 

type ProgressNotification struct {
	ProgressToken string  `json:"progressToken"`
	Progress      float64 `json:"progress"`
	Total         float64 `json:"total,omitempty"`
}

ProgressNotification reports progress for a long-running operation

type Prompt 

type Prompt struct {
	Name        string           `json:"name"`
	Description string           `json:"description,omitempty"`
	Arguments   []PromptArgument `json:"arguments,omitempty"`
}

Prompt represents an MCP prompt definition

type PromptArgument 

type PromptArgument struct {
	Name        string `json:"name"`
	Description string `json:"description,omitempty"`
	Required    bool   `json:"required,omitempty"`
}

PromptArgument describes a prompt parameter

type PromptListChangedNotification 

type PromptListChangedNotification struct{}

PromptListChangedNotification notifies that the prompt list has changed

type PromptListResult 

type PromptListResult struct {
	Prompts []Prompt `json:"prompts"`
}

PromptListResult is the response from prompts/list

type PromptMessage 

type PromptMessage struct {
	Role    string      `json:"role"`    // "user" or "assistant"
	Content interface{} `json:"content"` // Can be string or Content object
}

PromptMessage represents a message in a prompt

type PromptsCapability 

type PromptsCapability struct {
	ListChanged bool `json:"listChanged,omitempty"` // Sends list change notifications
}

type ReadResourceParams 

type ReadResourceParams struct {
	URI string `json:"uri"`
}

ReadResourceParams contains parameters for resources/read

type ReadResourceResult 

type ReadResourceResult struct {
	Contents []ResourceContents `json:"contents"`
}

ReadResourceResult is the response from resources/read

type Request 

type Request struct {
	JSONRPC string          `json:"jsonrpc"`          // Must be "2.0"
	ID      *RequestID      `json:"id,omitempty"`     // Null for notifications
	Method  string          `json:"method"`           // Method name
	Params  json.RawMessage `json:"params,omitempty"` // Method-specific params
}

Request represents a JSON-RPC 2.0 request

type RequestID 

type RequestID struct {
	Str *string
	Num *int64
}

RequestID can be string, number, or null per JSON-RPC 2.0 spec

func NewNumericRequestID 

func NewNumericRequestID(n int64) *RequestID

NewNumericRequestID creates a RequestID from a number

func NewStringRequestID 

func NewStringRequestID(s string) *RequestID

NewStringRequestID creates a RequestID from a string

func (*RequestID) MarshalJSON 

func (r *RequestID) MarshalJSON() ([]byte, error)

MarshalJSON implements json.Marshaler for RequestID

func (*RequestID) String 

func (r *RequestID) String() string

String returns a string representation of the RequestID

func (*RequestID) UnmarshalJSON 

func (r *RequestID) UnmarshalJSON(data []byte) error

UnmarshalJSON implements json.Unmarshaler for RequestID

type Resource 

type Resource struct {
	URI         string `json:"uri"`
	Name        string `json:"name"`
	Description string `json:"description,omitempty"`
	MimeType    string `json:"mimeType,omitempty"`
}

Resource represents an MCP resource definition

type ResourceContents 

type ResourceContents struct {
	URI      string                 `json:"uri"`
	MimeType string                 `json:"mimeType,omitempty"`
	Text     string                 `json:"text,omitempty"`
	Blob     string                 `json:"blob,omitempty"` // Base64
	Meta     map[string]interface{} `json:"_meta,omitempty"`
}

ResourceContents contains resource data

type ResourceListChangedNotification 

type ResourceListChangedNotification struct{}

ResourceListChangedNotification notifies that the resource list has changed

type ResourceListResult 

type ResourceListResult struct {
	Resources []Resource `json:"resources"`
}

ResourceListResult is the response from resources/list

type ResourceRef 

type ResourceRef struct {
	URI      string `json:"uri"`
	MimeType string `json:"mimeType,omitempty"`
}

ResourceRef references a resource

type ResourceTemplate 

type ResourceTemplate struct {
	URITemplate string `json:"uriTemplate"`
	Name        string `json:"name"`
	Description string `json:"description,omitempty"`
	MimeType    string `json:"mimeType,omitempty"`
}

ResourceTemplate defines a dynamic resource URI template

type ResourceUpdatedNotification 

type ResourceUpdatedNotification struct {
	URI string `json:"uri"`
}

ResourceUpdatedNotification notifies of a resource change

type ResourcesCapability 

type ResourcesCapability struct {
	Subscribe   bool `json:"subscribe,omitempty"`   // Supports subscriptions
	ListChanged bool `json:"listChanged,omitempty"` // Sends list change notifications
}

type Response 

type Response struct {
	JSONRPC string          `json:"jsonrpc"`          // Must be "2.0"
	ID      *RequestID      `json:"id"`               // Must match request
	Result  json.RawMessage `json:"result,omitempty"` // Success result
	Error   *Error          `json:"error,omitempty"`  // Error (mutually exclusive with Result)
}

Response represents a JSON-RPC 2.0 response

type RootsCapability 

type RootsCapability struct{}

Capability markers (empty structs indicate support)

type SamplingCapability 

type SamplingCapability struct{}

type SamplingParams 

type SamplingParams struct {
	Messages       []PromptMessage        `json:"messages"`
	ModelPrefs     *ModelPreferences      `json:"modelPreferences,omitempty"`
	SystemPrompt   string                 `json:"systemPrompt,omitempty"`
	IncludeContext string                 `json:"includeContext,omitempty"` // "none", "thisServer", "allServers"
	Temperature    *float64               `json:"temperature,omitempty"`
	MaxTokens      int                    `json:"maxTokens"`
	StopSequences  []string               `json:"stopSequences,omitempty"`
	Metadata       map[string]interface{} `json:"metadata,omitempty"`
}

SamplingParams contains parameters for sampling/createMessage

type SamplingResult 

type SamplingResult struct {
	Role       string  `json:"role"` // "assistant"
	Content    Content `json:"content"`
	Model      string  `json:"model"`
	StopReason string  `json:"stopReason,omitempty"` // "endTurn", "stopSequence", "maxTokens"
}

SamplingResult is the response from sampling/createMessage

type ServerCapabilities 

type ServerCapabilities struct {
	Tools     *ToolsCapability     `json:"tools,omitempty"`
	Resources *ResourcesCapability `json:"resources,omitempty"`
	Prompts   *PromptsCapability   `json:"prompts,omitempty"`
	Logging   *LoggingCapability   `json:"logging,omitempty"`
}

ServerCapabilities declares what the server supports

type Tool 

type Tool struct {
	Name        string                 `json:"name"`
	Description string                 `json:"description"`
	InputSchema map[string]interface{} `json:"inputSchema"`           // JSON Schema
	Annotations *ToolAnnotations       `json:"annotations,omitempty"` // MCP 2025-03-26
	Meta        map[string]interface{} `json:"_meta,omitempty"`       // MCP Apps metadata
}

Tool represents an MCP tool definition

type ToolAnnotations added in v1.2.0 

type ToolAnnotations struct {
	Title           string `json:"title,omitempty"`
	ReadOnlyHint    *bool  `json:"readOnlyHint,omitempty"`
	DestructiveHint *bool  `json:"destructiveHint,omitempty"`
	IdempotentHint  *bool  `json:"idempotentHint,omitempty"`
	OpenWorldHint   *bool  `json:"openWorldHint,omitempty"`
}

ToolAnnotations provides hints about tool behavior (MCP 2025-03-26)

type ToolListResult 

type ToolListResult struct {
	Tools []Tool `json:"tools"`
}

ToolListResult is the response from tools/list

type ToolsCapability 

type ToolsCapability struct{}

type UIResourceCSP added in v1.2.0 

type UIResourceCSP struct {
	ConnectDomains  []string `json:"connectDomains,omitempty"`
	ResourceDomains []string `json:"resourceDomains,omitempty"`
	FrameDomains    []string `json:"frameDomains,omitempty"`
	BaseURIDomains  []string `json:"baseUriDomains,omitempty"`
}

UIResourceCSP defines Content Security Policy settings for a UI resource.

type UIResourceMeta added in v1.2.0 

type UIResourceMeta struct {
	CSP           *UIResourceCSP         `json:"csp,omitempty"`
	Permissions   *UIResourcePermissions `json:"permissions,omitempty"`
	Domain        string                 `json:"domain,omitempty"`
	PrefersBorder *bool                  `json:"prefersBorder,omitempty"`
}

UIResourceMeta contains metadata for a UI resource's _meta field. It controls security policies, permissions, and display preferences.

type UIResourcePermissions added in v1.2.0 

type UIResourcePermissions struct {
	Camera         *struct{} `json:"camera,omitempty"`
	Microphone     *struct{} `json:"microphone,omitempty"`
	Geolocation    *struct{} `json:"geolocation,omitempty"`
	ClipboardWrite *struct{} `json:"clipboardWrite,omitempty"`
}

UIResourcePermissions declares what browser APIs a UI resource may use. Each permission is an opt-in marker (presence means requested).

type UIToolMeta added in v1.2.0 

type UIToolMeta struct {
	ResourceURI string   `json:"resourceUri,omitempty"` // URI of associated UI resource (e.g. "ui://loom/conversation-viewer")
	Visibility  []string `json:"visibility,omitempty"`  // Who sees this tool: "model", "app"
}

UIToolMeta contains UI-related metadata attached to a tool's _meta field. When present, it indicates the tool has an associated interactive UI resource.

func GetUIToolMeta added in v1.2.0 

func GetUIToolMeta(tool Tool) *UIToolMeta

GetUIToolMeta extracts UI metadata from a Tool's _meta field. Returns nil if the tool has no UI metadata.

Source Files

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