KWDB MCP Server

KWDB MCP Server

中文版

Overview

The KWDB MCP Server is a server implementation based on the MCP (Model Context Protocol) protocol, which provides a set of tools and resources for interacting with the KWDB database and providing business intelligence functionality through the MCP protocol. The KWDB MCP Server supports reading, writing, querying, modifying data, and performing DDL operations.

Architecture

The core process of the KWDB MCP Server consists of the following components:

• Parse MCP protocol: deal with MCP StdIO or HTTP SSE requests.
• Schedule MCP Tools: distribute API requests based on the types of MCP Tools.
• Prepare queries: automatically add the LIMIT 20 clause for SQL queries without a LIMIT clause.
• Format query results: adopt a consistent JSON format for all API responses.

Features

• Read Operations: execute SELECT, SHOW, EXPLAIN, and other read-only queries.
• Write Operations: execute INSERT, UPDATE, DELETE, and CREATE, DROP, ALTER DDL operations.
• Database Information: get information about the database, including tables and their schemas.
• Inspection Tools: query-metrics (fixed catalog of 32 runtime metrics against the admin /restapi/ts/query endpoint) and query-slow-sql (top-N slow SQL statements via a SELECT against kwdb_internal.node_statement_statistics) — both derive credentials from the existing DB URL, supporting both TLS and insecure KaiwuDB deployments.
• Syntax Guide: access a comprehensive syntax guide for KWDB through Prompts.
• Standard API Response: provide consistent error handling mechanisms.
  • Tools Error: error information is wrapped in result objects with isError flag.

  {
    "content": [{"type": "text", "text": "Query error: error details"}],
    "isError": true
  }
  

  • Resources Error: return standard JSON-RPC error responses directly.

  {
    "jsonrpc": "2.0",
    "id": 1,
    "error": {
      "code": -32002,  // RESOURCE_NOT_FOUND: resource does not exist
      "message": "handler not found for resource URI 'kwdb://table/nonexistent': resource not found"
    }
  }
  

  Or internal processing errors:

  {
    "jsonrpc": "2.0",
    "id": 1,
    "error": {
      "code": -32603,  // INTERNAL_ERROR: internal resource processing error
      "message": "failed to get table schema for 'tablename': database connection error"
    }
  }
  

  • Success Response: tools return result objects, resources return content arrays.
• Automatic LIMIT: prevent large result sets by automatically adding the LIMIT 20 clause to SELECT queries without a LIMIT clause.

Security

The KWDB MCP Server provides the following security measures:

• Provide separate tools for read and write operations.
• Valid queries to ensure that they match the expected operation type.
• Print clear error messages for unauthorized operations.

MCP Resources

MCP Resources allow the KWDB MCP Server to expose data and content that can be read by MCP clients and used as context for LLM interactions. The KWDB MCP Server provides the following MCP Resources:

Resources	URI Format	Description	Example
Product information	kwdb://product_info	Product information, including the version and supported features	kwdb://product_info/
Database metadata	kwdb://db_info/{database_name}	Information about a specific database, including the engine type, comments, and tables	kwdb://db_info/db_shig
Table schema	kwdb://table/{table_name}	Schema of a specific table, including columns and example queries	kwdb://table/user_profile

MCP Tools

The MCP Tools enable the KWDB MCP Server to expose executable functionality to MCP clients. Through MCP Tools, LLMs can interact with external systems. The KWDB MCP Server provides the following MCP Tools.

read-query

The KWDB MCP Server executes the SELECT, SHOW, EXPLAIN statements, and other read-only queries to read data from the database. The read_query function returns the query results in a format of array for your SQL statement. In addition, the KWDB MCP Server will automatically add the LIMIT 20 clause to SELECT queries without a LIMIT clause to prevent large result sets.

Examples:

-- Query table data.
SELECT * FROM users LIMIT 10;

-- List all created tables.
SHOW TABLES;

-- Execute a SQL query and generate details about the SQL query.
EXPLAIN ANALYZE SELECT * FROM orders WHERE user_id = 1;

write-query

The KWDB MCP Server executes data modification queries, including DML and DDL operations.

Examples:

-- Insert data into the table.
INSERT INTO users (name, email) VALUES ('John Doe', '[email protected]');

-- Update data in the table.
UPDATE users SET email = '[email protected]' WHERE id = 1;

-- Remove data from the table.
DELETE FROM users WHERE id = 1;

-- Create a table.
CREATE TABLE products (id SERIAL PRIMARY KEY, name TEXT, price DECIMAL);

-- Add a column to a table.
ALTER TABLE products ADD COLUMN description TEXT;

-- Remove a table.
DROP TABLE products;

query-metrics

The KWDB MCP Server can query historical runtime metrics through the database admin /ts/query API. The tool accepts a fixed catalog of 32 inspection metrics (QPS, CPU, memory, latency, storage, cluster, network) defined in docs/design-tls-inspection-tools.md. Each call requires metric_names, start_ms, end_ms, and sample_ms. Basic Auth credentials are derived from the connection string's user:password.

The 32-metric catalog spans these categories (all derivative: "none"):

Category	Examples
Basic	cr.node.liveness.livenodes, cr.node.sys.uptime
System	cr.node.sys.cpu.user.percent, cr.store.capacity, cr.node.sys.rss
SQL workload	cr.node.sql.query.count, cr.node.exec.latency-p99
Storage	cr.store.totalbytes, cr.store.livebytes
Cluster	cr.store.replicas, cr.store.ranges.unavailable
Network	cr.node.clock-offset.meannanos

Examples:

{
  "metric_names": ["cr.node.sql.query.count", "cr.node.sys.cpu.user.percent"],
  "start_ms": 1775035140000,
  "end_ms": 1775035740000,
  "sample_ms": 60000
}

Successful response (the upstream /ts/query returns code: 0 on success):

{
  "status": "success",
  "type": "metrics_inspection",
  "data": {
    "code": 0,
    "desc": ""
  },
  "error": null
}

query-slow-sql

The KWDB MCP Server can query slow SQL statements by running a SELECT against the cluster-side system table kwdb_internal.node_statement_statistics. The tool accepts optional limit (default 10), min_latency_ms (default 0), and sort_by (default service_lat; supports run_lat, plan_lat, count). Results include query text, four latency fields (in milliseconds), and execution count.

Filtering always runs against service_latency_ms, regardless of the chosen sort_by. The default call returns the top 10 statements sorted by mean service latency.

Examples:

{
  "limit": 10,
  "min_latency_ms": 100,
  "sort_by": "service_lat"
}

Successful response (truncated for brevity):

{
  "data": [
    {
      "id": "1",
      "fingerprint": "1",
      "query": "SELECT count(_), max(\"timestamp\") FROM [DELETE FROM system.rangelog WHERE ...]",
      "service_latency_ms": 3.805022,
      "run_latency_ms": 0.649384,
      "plan_latency_ms": 1.041746,
      "count": 1
    }
  ],
  "status": "success",
  "type": "slow_sql_inspection"
}

Both query-metrics and query-slow-sql reuse the same X-Database-URI header (or default pool) and derive their Basic Auth from the saved credentials; the admin endpoint URL is auto-derived from the DB URL's host. TLS endpoints skip certificate verification to match the KaiwuDB self-signed convention.

MCP Prompts

MCP Prompts enable the KWDB MCP Server to define reusable prompt templates and workflows that MCP clients can easily surface to users and LLMs. They provide a powerful way to standardize and share common LLM interactions. The KWDB MCP Server provides the following MCP Prompts:

Type	Prompt Name	Description
Database description	db_description	A comprehensive description of KWDB database, including core functions, supported features, and use cases.
Syntax guide	syntax_guide	A comprehensive syntax guide for KWDB, including examples of common queries and best practices.
Cluster management	cluster_management	A comprehensive guide for managing KWDB clusters, including node management, load balancing, and monitoring.
Data migration	data_migration	A guide for migrating data to and from KWDB, including import/export methods and best practices.
Installation	installation	A step-by-step guide for installing and deploying KWDB in various environments.
Performance tunning	performance_tuning	A guide for optimizing KWDB performance, including query optimization, indexing strategies, and system-level tuning.
Troubleshooting	troubleshooting	A guide for diagnosing and resolving common KWDB issues and errors.
Backup and restore	backup_restore	A comprehensive guide for backing up and restoring KWDB databases, including strategies, tools, and best practices.
DBA templates	dba_template	Templates and guidelines for MCP Prompts writing.

Add MCP Prompts

The MCP Prompts are Markdown files stored in the pkg/prompts/docs/ directory. These files are embedded into the binary when compiling the KWDB MCP Server using Go's embed package. Currently, the KWDB MCP Server provides the following Prompts files:

• pkg/prompts/docs/ReadExamples.md: contain read query examples (using the SELECT statement).
• pkg/prompts/docs/WriteExamples.md: contain write query examples (using the INSERT, UPDATE, DELETE, CREATE, ALTER statements).
• pkg/prompts/docs/DBDescription.md: contain the database description.
• pkg/prompts/docs/SyntaxGuide.md: contain the SQL syntax guide.
• pkg/prompts/docs/ClusterManagementGuide.md: contain the cluster management guide.
• pkg/prompts/docs/DataMigrationGuide.md: contain the data migration guide.
• pkg/prompts/docs/InstallationGuide.md: contain the installation guide.
• pkg/prompts/docs/PerformanceTuningGuide.md: contain the performance tuning guide.
• pkg/prompts/docs/TroubleShootingGuide.md: contain the troubleshooting guide.
• pkg/prompts/docs/BackupRestoreGuide.md: contain the backup and restore guide.
• pkg/prompts/docs/DBATemplate.md: contain the database administration template.

To add MCP Prompts, follow these steps:

1. Create a Markdown file in the pkg/prompts/docs/ directory, such as new_usecase.md.
2. Add the variable and load codes in the pkg/prompts/prompts.go file.
3. Create a registration function for the new MCP Prompts.
4. Add the registration function call to registerUseCasePrompts() in the pkg/prompts/prompts.go file.
5. Update the README file.

For details about how to add MCP Prompts, see comments in the pkg/prompts/prompts.go file.

Modify MCP Prompts

To modify MCP Prompts, follow these steps:

1. Edit the specific Markdown file(s) in the pkg/prompts/docs/ directory.
2. Run the make build command to rebuild the application. The updated MCP Prompts will be embedded in the binary.

Build From Source Code

Prerequisites

• Install Go 1.23 or higher.
• Download and install PostgreSQL Driver lib/pq.
• Install and start KWDB, configure the authentication method, and create a database. For details, see the KWDB Documentation Website.
• Create a user with appropriate privileges on tables and databases. For details, see Create Users.

Steps

1. Clone the repository.

   git clone https://gitee.com/kwdb/kwdb-mcp-server
   cd kwdb-mcp-server
   

2. Install dependencies.

   make deps
   

3. Build the application.

   make build
   

If you succeed, the application adopts the following structure.

kwdb-mcp-server/
├── bin/
│   └── kwdb-mcp-server      # Binary executable file
├── cmd/
│   └── kwdb-mcp-server/
│       └── main.go           # The main application
├── pkg/
│   ├── db/
│   │   └── db.go             # Database operations
│   ├── prompts/
│   │   ├── prompts.go        # MCP Prompts
│   │   └── docs/             # MCP Prompts files
│   │       ├── ReadExamples.md     # Read query examples
│   │       ├── WriteExamples.md    # Write query examples
│   │       ├── DBDescription.md    # Database descriptions
│   │       ├── SyntaxGuide.md      # SQL Syntax guide
│   │       ├── ClusterManagementGuide.md # Cluster management guide
│   │       ├── DataMigrationGuide.md    # Data migration guide
│   │       ├── InstallationGuide.md      # Installation guide
│   │       ├── PerformanceTuningGuide.md # Performance tunning
│   │       ├── TroubleShootingGuide.md   # Troubleshooting guide
│   │       ├── BackupRestoreGuide.md     # Backup and restore guide
│   │       └── DBATemplate.md            # DBA templates
│   ├── resources/
│   │   └── resources.go      # MCP Resources
│   ├── server/
│   │   └── server.go         # KWDB MCP Server configurations
│   ├── tools/
│   │   └── tools.go          # MCP Tools
│   └── version/
│       └── version.go        # Version information
├── Makefile                  # Commands for building and running the KWDB MCP Server
└── README.md                 # README file

Start KWDB MCP Server

The KWDB MCP Server supports three transport modes:

• StdIO (Standard Input/Output) mode: Uses standard input/output for communication. This is the default mode.
• HTTP mode (Recommended): Uses HTTP for communication. This is the recommended mode for production.
• SSE (Server-Sent Events) mode (Deprecated): Uses HTTP POST and SSE for communication. This mode will be deprecated soon.

Operating modes

• Single-DB (compatibility): Start the server with an optional PostgreSQL connection string as the first argument (or via CONNECTION_STRING in the Makefile). The server initializes a default connection pool. Tools read-query and write-query may be called without the X-Database-URI header; they use this default pool.
• Stateless multi-tenant: Start the server without a connection string (e.g. ./bin/kwdb-mcp-server or ./bin/kwdb-mcp-server -t http -p 8080). The server does not open any database until a tool is invoked. Every read-query and write-query call must send the request header X-Database-URI with a full PostgreSQL connection string; otherwise the tool returns an error: missing X-Database-URI header.
• Admin endpoint auto-derived: Inspection tools (query-metrics, query-slow-sql) derive the admin endpoint URL from the connection string's host (default port 8080) and derive Basic Auth credentials from the same connection string. No separate admin configuration is needed; the connection string's sslmode and cert paths determine whether the admin endpoint is reached over http or https. To override the derived admin URL on a per-request basis, send X-Admin-Base-URL.

---

StdIO Mode

• Run the KWDB MCP Server (with an optional connection string for single-DB mode):

  ./bin/kwdb-mcp-server "postgresql://<username>:<password>@<hostname>:<port>/<database_name>?sslmode=disable"
  

• Or run without a connection string for stateless mode; then each read-query / write-query call must send the X-Database-URI header. Inspection tools (query-metrics, query-slow-sql) automatically derive the admin endpoint URL and Basic Auth from this same connection string; send X-Admin-Base-URL to override the derived URL.

  ./bin/kwdb-mcp-server
  

• Run the KWDB MCP Server using the Makefile:

  CONNECTION_STRING="postgresql://<username>:<password>@<hostname>:<port>/<database_name>?sslmode=disable" make run
  

Parameters:

• username: Username for connecting to the KWDB database.
• password: Password for authentication.
• hostname: IP address of the KWDB database.
• port: Port for connecting to the KWDB database.
• database_name: Name of the KWDB database to access.
• sslmode: SSL mode. Supported values: disable, allow, prefer, require, verify-ca, verify-full. For details, see SSL Mode Parameters.

---

HTTP Mode (Recommended)

• Run the KWDB MCP Server in HTTP mode:

  CONNECTION_STRING="postgresql://<username>:<password>@<hostname>:<port>/<database_name>?sslmode=disable" PORT=8080 make run-http
  

• The HTTP service listens on 0.0.0.0:<port> by default, and the MCP endpoint is http://<host>:<port>/mcp. When started without a connection string (stateless mode), clients must send the X-Database-URI request header with each read-query / write-query call.

• The inspection tools (query-metrics, query-slow-sql) derive Basic Auth and the admin endpoint URL from the X-Database-URI connection string; send X-Admin-Base-URL to override the derived URL.

• HTTPS (TLS) is optional: pass both --tls-cert and --tls-key with PEM file paths. The server then listens with TLS; the MCP endpoint is https://<host>:<port>/mcp. If only one of the two flags is set, the process exits with an error. TLS is implemented via mcp-go WithTLSCert (requires mcp-go v0.39+).

  ./bin/kwdb-mcp-server -t http -p 8443 --tls-cert /path/to/cert.pem --tls-key /path/to/key.pem "postgresql://..."
  

Parameters:

• -t or --transport: Transport type, supports stdio, sse, http.
  • stdio: Standard input/output mode
  • sse: SSE mode (deprecated)
  • http: HTTP mode (recommended)
• -p or --port: Listening port for KWDB MCP Server, default is 8080.
• --tls-cert / --tls-key: Optional. PEM certificate and private key for HTTP mode HTTPS. Both must be set together; only applies when -t http.
• username: Username for connecting to the KWDB database.
• password: Password for authentication.
• hostname: IP address of the KWDB database.
• port: Port for connecting to the KWDB database.
• database_name: Name of the KWDB database to access.
• sslmode: SSL mode. Supported values: disable, allow, prefer, require, verify-ca, verify-full. For details, see SSL Mode Parameters.

---

SSE Mode (Deprecated)

Note

SSE mode is deprecated and will be removed in future releases. Please use HTTP mode if possible.

• Run the KWDB MCP Server in SSE mode (or omit CONNECTION_STRING for stateless mode; then clients must send X-Database-URI with each tool call):

  CONNECTION_STRING="postgresql://<username>:<password>@<hostname>:<port>/<database_name>?sslmode=disable" PORT=8080 make run-sse
  

Parameters:

• -t or --transport: Transport type, supports stdio, sse, http.
  • stdio: Standard input/output mode
  • sse: SSE mode (deprecated)
  • http: HTTP mode (recommended)
• -p or --port: Listening port for KWDB MCP Server, default is 8080.
• username: Username for connecting to the KWDB database.
• password: Password for authentication.
• hostname: IP address of the KWDB database.
• port: Port for connecting to the KWDB database.
• database_name: Name of the KWDB database to access.
• sslmode: SSL mode. Supported values: disable, allow, prefer, require, verify-ca, verify-full. For details, see SSL Mode Parameters.

Integrate with LLM Agents

For details about how the KWDB MCP Server integerates with LLM Agents, see Integrate with LLM Agents.

Troubleshooting

For details about how to troubleshoot the KWDB MCP Server, see Troubleshooting.

Documentation

For documentation about the KWDB MCP Server, see the KWDB Documentation Website.

Future Enhancements

• Query history: implement query history functionality.
• Remote mode: support connecting to the remote KWDB MCP Server.
• Improved optimization suggestions: enhance query optimization recommendations.
• Metrics resource: aAdd database metrics.

Contribution

Contributions are welcome! Please feel free to submit issues and pull requests.

License

This project is licensed under the MIT License.

Acknowledgements

• mark3labs/mcp-go - MCP Go server framework
• lib/pq - PostgreSQL Go driver

Other

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