database_mcp_postgres/tools/
read_query.rs

1//! MCP tool: `read_query`.
2
3use std::borrow::Cow;
4
5use database_mcp_server::AppError;
6use database_mcp_server::types::{QueryRequest, QueryResponse};
7use database_mcp_sql::timeout::execute_with_timeout;
8use database_mcp_sql::validation::validate_read_only_with_dialect;
9use rmcp::handler::server::router::tool::{AsyncTool, ToolBase};
10use rmcp::model::{ErrorData, ToolAnnotations};
11use serde_json::Value;
12use sqlx::postgres::PgRow;
13use sqlx_to_json::RowExt;
14
15use crate::PostgresHandler;
16
17/// Marker type for the `read_query` MCP tool.
18pub(crate) struct ReadQueryTool;
19
20impl ReadQueryTool {
21    const NAME: &'static str = "read_query";
22    const DESCRIPTION: &'static str = "Execute a read-only SQL query (SELECT, SHOW, DESCRIBE, USE, EXPLAIN).";
23}
24
25impl ToolBase for ReadQueryTool {
26    type Parameter = QueryRequest;
27    type Output = QueryResponse;
28    type Error = ErrorData;
29
30    fn name() -> Cow<'static, str> {
31        Self::NAME.into()
32    }
33
34    fn description() -> Option<Cow<'static, str>> {
35        Some(Self::DESCRIPTION.into())
36    }
37
38    fn annotations() -> Option<ToolAnnotations> {
39        Some(
40            ToolAnnotations::new()
41                .read_only(true)
42                .destructive(false)
43                .idempotent(true)
44                .open_world(true),
45        )
46    }
47}
48
49impl AsyncTool<PostgresHandler> for ReadQueryTool {
50    async fn invoke(handler: &PostgresHandler, params: Self::Parameter) -> Result<Self::Output, Self::Error> {
51        Ok(handler.read_query(&params).await?)
52    }
53}
54
55impl PostgresHandler {
56    /// Executes a read-only SQL query.
57    ///
58    /// Validates that the query is read-only before executing.
59    ///
60    /// # Errors
61    ///
62    /// Returns [`AppError::ReadOnlyViolation`] if the query is not
63    /// read-only, or [`AppError::Query`] if the backend reports an error.
64    pub async fn read_query(&self, request: &QueryRequest) -> Result<QueryResponse, AppError> {
65        validate_read_only_with_dialect(&request.query, &sqlparser::dialect::PostgreSqlDialect {})?;
66        let db = Some(request.database_name.trim()).filter(|s| !s.is_empty());
67        let pool = self.get_pool(db).await?;
68        let rows: Vec<PgRow> = execute_with_timeout(
69            self.config.query_timeout,
70            &request.query,
71            sqlx::query(&request.query).fetch_all(&pool),
72        )
73        .await?;
74        Ok(QueryResponse {
75            rows: Value::Array(rows.iter().map(RowExt::to_json).collect()),
76        })
77    }
78}
database_mcp_postgres/tools/read_query.rs

database_mcp_postgres/tools/
read_query.rs
