177 lines
No EOL
4.1 KiB
Text
177 lines
No EOL
4.1 KiB
Text
---
|
|
title: Logging
|
|
description: "MCP protocol specification for server logging capabilities"
|
|
---
|
|
|
|
Logging enables servers to send log messages to clients in a structured way. Clients can control the verbosity of logging by setting the minimum log level they want to receive. Each log message includes a level indicating its severity, an optional logger name for organization, and arbitrary data that can be any JSON-serializable value.
|
|
|
|
## Capabilities
|
|
|
|
To indicate support for the Logging API, servers MUST include a `logging` capability in their `ServerCapabilities` during initialization. The `logging` capability SHOULD be an empty object:
|
|
|
|
```json
|
|
{
|
|
"capabilities": {
|
|
"logging": {}
|
|
}
|
|
}
|
|
```
|
|
|
|
Clients SHOULD check for this capability before attempting to set the log level.
|
|
|
|
## Concepts
|
|
|
|
### Log Levels
|
|
|
|
MCP defines the following log levels in order of increasing severity:
|
|
|
|
- `debug`: Detailed information for debugging
|
|
- `info`: General informational messages
|
|
- `notice`: Normal but significant events
|
|
- `warning`: Warning conditions
|
|
- `error`: Error conditions
|
|
- `critical`: Critical conditions
|
|
- `alert`: Action must be taken immediately
|
|
- `emergency`: System is unusable
|
|
|
|
These levels correspond to syslog severity levels as defined in [RFC 5424](https://datatracker.ietf.org/doc/html/rfc5424#section-6.2.1).
|
|
|
|
### Log Messages
|
|
|
|
Each log message contains:
|
|
- A severity level
|
|
- Optional logger name for categorization
|
|
- Arbitrary data payload (any JSON-serializable value)
|
|
|
|
## Use Cases
|
|
|
|
Common use cases for logging include:
|
|
|
|
### Informational Updates
|
|
|
|
```json
|
|
{
|
|
"level": "info",
|
|
"logger": "file_processor",
|
|
"data": "Processing file: example.txt"
|
|
}
|
|
```
|
|
|
|
### Transient errors
|
|
|
|
```json
|
|
{
|
|
"level": "error",
|
|
"logger": "git_clone",
|
|
"data": {
|
|
"error": "Remote repository temporarily unreachable",
|
|
"details": {
|
|
"repository": "github.com/example/repo",
|
|
"attempt": 2,
|
|
"maxAttempts": 3,
|
|
"willRetry": true,
|
|
"retryIn": "5s"
|
|
}
|
|
}
|
|
}
|
|
```
|
|
|
|
## Diagram
|
|
|
|
The following diagram visualizes the logging interaction between client and server:
|
|
|
|
```mermaid
|
|
sequenceDiagram
|
|
participant Client
|
|
participant Server
|
|
|
|
Note over Client,Server: Configure logging
|
|
Client->>Server: logging/setLevel (info)
|
|
Server-->>Client: EmptyResult
|
|
|
|
Note over Client,Server: Server sends log messages
|
|
Server--)Client: notifications/message (info)
|
|
Server--)Client: notifications/message (error)
|
|
```
|
|
|
|
## Messages
|
|
|
|
This section defines the protocol messages for logging in the Model Context Protocol (MCP).
|
|
|
|
### Setting Log Level
|
|
|
|
#### Request
|
|
|
|
To configure the minimum log level to receive, the client MUST send a `logging/setLevel` request.
|
|
|
|
Method: `logging/setLevel`
|
|
Params:
|
|
- `level`: The minimum severity level of logs to receive (string, required)
|
|
|
|
Example:
|
|
```json
|
|
{
|
|
"jsonrpc": "2.0",
|
|
"id": 1,
|
|
"method": "logging/setLevel",
|
|
"params": {
|
|
"level": "info"
|
|
}
|
|
}
|
|
```
|
|
|
|
#### Response
|
|
|
|
The server MUST respond with an empty result if successful:
|
|
|
|
```json
|
|
{
|
|
"jsonrpc": "2.0",
|
|
"id": 1,
|
|
"result": {}
|
|
}
|
|
```
|
|
|
|
### Log Message Notification
|
|
|
|
The server sends log messages to the client using the `notifications/message` notification.
|
|
|
|
Method: `notifications/message`
|
|
Params:
|
|
- `level`: The severity level of the message (string, required)
|
|
- `logger`: Optional name of the logger (string)
|
|
- `data`: The log message data (any JSON-serializable value, required)
|
|
|
|
Example:
|
|
```json
|
|
{
|
|
"jsonrpc": "2.0",
|
|
"method": "notifications/message",
|
|
"params": {
|
|
"level": "error",
|
|
"logger": "database",
|
|
"data": {
|
|
"error": "Connection failed",
|
|
"details": {
|
|
"host": "localhost",
|
|
"port": 5432
|
|
}
|
|
}
|
|
}
|
|
}
|
|
```
|
|
|
|
## Error Handling
|
|
|
|
Clients MUST be prepared to handle:
|
|
- Invalid log levels in setLevel requests
|
|
- Missing or malformed log message parameters
|
|
- Unexpected data types in log messages
|
|
|
|
## Security Considerations
|
|
|
|
Implementations MUST carefully consider:
|
|
- Sanitizing sensitive information from log messages
|
|
- Rate limiting log messages to prevent flooding
|
|
- Access control for log configuration
|
|
- Validation of log data to prevent injection attacks |