{
"RequestId": "string | number",
"ProgressToken": "string | number",
"Cursor": "string",
"Role": "user | assistant",
"LogLevel": "debug | info | notice | warning | error | critical | alert | emergency"
}{
"Annotations": {
"audience": ["user", "assistant"],
"priority": 0.8
},
"TextContent": {
"type": "text",
"text": "content here",
"annotations": { "Annotations" }
},
"ImageContent": {
"type": "image",
"data": "base64_encoded_data",
"mimeType": "image/png",
"annotations": { "Annotations" }
},
"AudioContent": {
"type": "audio",
"data": "base64_encoded_data",
"mimeType": "audio/wav",
"annotations": { "Annotations" }
},
"EmbeddedResource": {
"type": "resource",
"resource": { "TextResource | BlobResource" },
"annotations": { "Annotations" }
}
}{
"PromptMessage": {
"role": "user | assistant",
"content": { "TextContent | ImageContent | AudioContent | EmbeddedResource" }
},
"SamplingMessage": {
"role": "user | assistant",
"content": { "TextContent | ImageContent | AudioContent" }
}
}{
"JSONRPCRequest": {
"jsonrpc": "2.0",
"id": "RequestId",
"method": "string",
"params": {
"_meta": {
"progressToken": "ProgressToken"
}
}
},
"JSONRPCResponse": {
"jsonrpc": "2.0",
"id": "RequestId",
"result": {},
"_meta": {}
},
"JSONRPCError": {
"jsonrpc": "2.0",
"id": "RequestId",
"error": {
"code": -32000,
"message": "Error description",
"data": {}
}
},
"JSONRPCNotification": {
"jsonrpc": "2.0",
"method": "string",
"params": {
"_meta": {}
}
}
}{
"ClientCapabilities": {
"roots": {
"listChanged": true
},
"sampling": {},
"experimental": {}
},
"ServerCapabilities": {
"prompts": {
"listChanged": true
},
"resources": {
"listChanged": true,
"subscribe": true
},
"tools": {
"listChanged": true
},
"logging": {},
"completions": {},
"experimental": {}
}
}{
"InitializeRequest": {
"method": "initialize",
"params": {
"protocolVersion": "2024-11-05",
"clientInfo": {
"name": "client-name",
"version": "1.0.0"
},
"capabilities": { "ClientCapabilities" }
}
},
"InitializeResult": {
"protocolVersion": "2024-11-05",
"serverInfo": {
"name": "server-name",
"version": "1.0.0"
},
"capabilities": { "ServerCapabilities" },
"instructions": "Optional LLM hints"
},
"InitializedNotification": {
"method": "notifications/initialized",
"params": {}
}
}{
"Resource": {
"name": "resource-name",
"uri": "file://path/to/resource",
"description": "What this resource contains",
"mimeType": "text/plain",
"size": 1024,
"annotations": { "Annotations" }
},
"ResourceTemplate": {
"name": "template-name",
"uriTemplate": "file://path/{id}",
"description": "Template description",
"mimeType": "text/plain",
"annotations": { "Annotations" }
},
"ListResourcesRequest": {
"method": "resources/list",
"params": {
"cursor": "optional_cursor"
}
},
"ReadResourceRequest": {
"method": "resources/read",
"params": {
"uri": "file://path/to/resource"
}
},
"SubscribeRequest": {
"method": "resources/subscribe",
"params": {
"uri": "file://path/to/resource"
}
}
}{
"Tool": {
"name": "tool-name",
"description": "What this tool does",
"inputSchema": {
"type": "object",
"properties": {
"param1": { "type": "string" },
"param2": { "type": "number" }
},
"required": ["param1"]
},
"annotations": {
"title": "Human readable title",
"readOnlyHint": false,
"destructiveHint": true,
"idempotentHint": false,
"openWorldHint": true
}
},
"CallToolRequest": {
"method": "tools/call",
"params": {
"name": "tool-name",
"arguments": {
"param1": "value1",
"param2": 42
}
}
},
"CallToolResult": {
"content": [
{ "type": "text", "text": "Tool output" }
],
"isError": false,
"_meta": {}
}
}{
"PromptArgument": {
"name": "arg-name",
"description": "Argument description",
"required": true
},
"Prompt": {
"name": "prompt-name",
"description": "Prompt description",
"arguments": [{ "PromptArgument" }]
},
"GetPromptRequest": {
"method": "prompts/get",
"params": {
"name": "prompt-name",
"arguments": {
"arg1": "value1",
"arg2": "value2"
}
}
},
"GetPromptResult": {
"description": "Prompt description",
"messages": [
{
"role": "user",
"content": { "type": "text", "text": "Prompt content" }
}
]
}
}{
"ModelHint": {
"name": "claude-3-5-sonnet"
},
"ModelPreferences": {
"costPriority": 0.3,
"speedPriority": 0.5,
"intelligencePriority": 0.9,
"hints": [{ "ModelHint" }]
},
"CreateMessageRequest": {
"method": "sampling/createMessage",
"params": {
"messages": [{ "SamplingMessage" }],
"maxTokens": 1000,
"systemPrompt": "You are a helpful assistant",
"temperature": 0.7,
"stopSequences": ["END"],
"modelPreferences": { "ModelPreferences" },
"metadata": {},
"includeContext": "thisServer"
}
},
"CreateMessageResult": {
"role": "assistant",
"content": { "type": "text", "text": "LLM response" },
"model": "claude-3-5-sonnet-20241022",
"stopReason": "stop_sequence"
}
}{
"CompleteRequest": {
"method": "completion/complete",
"params": {
"ref": {
"type": "ref/prompt",
"name": "prompt-name"
},
"argument": {
"name": "arg-name",
"value": "partial_value"
}
}
},
"CompleteResult": {
"completion": {
"values": ["completion1", "completion2"],
"total": 50,
"hasMore": true
}
}
}{
"Root": {
"uri": "file:///path/to/directory",
"name": "project-root"
},
"ListRootsRequest": {
"method": "roots/list",
"params": {}
},
"ListRootsResult": {
"roots": [{ "Root" }]
}
}{
"ResourceListChangedNotification": {
"method": "notifications/resources/list_changed",
"params": {}
},
"ResourceUpdatedNotification": {
"method": "notifications/resources/updated",
"params": {
"uri": "file://path/to/resource"
}
},
"ProgressNotification": {
"method": "notifications/progress",
"params": {
"progressToken": "token123",
"progress": 50,
"total": 100,
"message": "Processing..."
}
},
"LoggingMessageNotification": {
"method": "notifications/message",
"params": {
"level": "info",
"data": "Log message",
"logger": "server.component"
}
},
"CancelledNotification": {
"method": "notifications/cancelled",
"params": {
"requestId": "req123",
"reason": "User cancelled"
}
}
}{
"PaginatedRequest": {
"method": "resources/list",
"params": {
"cursor": "opaque_cursor_string"
}
},
"PaginatedResult": {
"resources": [{ "Resource" }],
"nextCursor": "next_cursor_string",
"_meta": {}
}
}Critical implementation requirements
- Initialization:
initialize→initialize_result→notifications/initialized(required sequence) - Progress: Optional out-of-band notifications using
progressToken - Errors: Tool errors in
CallToolResult.isError, protocol errors as JSON-RPC errors - Pagination: Use opaque cursors, max reasonable page sizes
- Cancellation: Either side can cancel with
requestId - Notifications: No response expected, may arrive without subscription
| Component | Constraint | Details |
|---|---|---|
_meta fields |
Reserved | Protocol extensions only |
| Binary data | Base64 | Always encoded in JSON strings |
| URI schemes | file:// |
Required for roots, others server-dependent |
| JSON Schema | Object only | Tool inputs must be object type |
| Versioning | Negotiated | Client/server agree on compatible version |
| Threading | Single connection | Async via JSON-RPC batching |
{
"Core": ["initialize", "ping"],
"Resources": ["resources/list", "resources/templates/list", "resources/read", "resources/subscribe", "resources/unsubscribe"],
"Prompts": ["prompts/list", "prompts/get"],
"Tools": ["tools/list", "tools/call"],
"Completion": ["completion/complete"],
"Logging": ["logging/setLevel"]
}{
"Core": ["ping"],
"Sampling": ["sampling/createMessage"],
"Roots": ["roots/list"]
}