database_mcp_postgres/tools/
list_tables.rs

1//! MCP tool: `list_tables`.
2
3use std::borrow::Cow;
4
5use database_mcp_server::AppError;
6use database_mcp_server::types::{ListTablesRequest, ListTablesResponse};
7use database_mcp_sql::Connection as _;
8use rmcp::handler::server::router::tool::{AsyncTool, ToolBase};
9use rmcp::model::{ErrorData, ToolAnnotations};
10use serde_json::Value;
11
12use crate::PostgresHandler;
13
14/// Marker type for the `list_tables` MCP tool.
15pub(crate) struct ListTablesTool;
16
17impl ListTablesTool {
18    const NAME: &'static str = "list_tables";
19    const DESCRIPTION: &'static str = r#"List all tables in a specific database. Requires `database_name` — call `list_databases` first to discover available databases.
20
21<usecase>
22Use when:
23- Exploring a database to find relevant tables
24- Verifying a table exists before querying or inspecting it
25- The user asks what tables are in a database
26</usecase>
27
28<examples>
29✓ "What tables are in the mydb database?" → list_tables(database_name="mydb")
30✓ "Does a users table exist?" → list_tables to check
31✗ "Show me the columns of users" → use get_table_schema instead
32</examples>
33
34<what_it_returns>
35A sorted JSON array of table name strings.
36</what_it_returns>"#;
37}
38
39impl ToolBase for ListTablesTool {
40    type Parameter = ListTablesRequest;
41    type Output = ListTablesResponse;
42    type Error = ErrorData;
43
44    fn name() -> Cow<'static, str> {
45        Self::NAME.into()
46    }
47
48    fn description() -> Option<Cow<'static, str>> {
49        Some(Self::DESCRIPTION.into())
50    }
51
52    fn annotations() -> Option<ToolAnnotations> {
53        Some(
54            ToolAnnotations::new()
55                .read_only(true)
56                .destructive(false)
57                .idempotent(true)
58                .open_world(false),
59        )
60    }
61}
62
63impl AsyncTool<PostgresHandler> for ListTablesTool {
64    async fn invoke(handler: &PostgresHandler, params: Self::Parameter) -> Result<Self::Output, Self::Error> {
65        Ok(handler.list_tables(&params).await?)
66    }
67}
68
69impl PostgresHandler {
70    /// Lists all tables in a database.
71    ///
72    /// # Errors
73    ///
74    /// Returns [`AppError`] if the identifier is invalid or the query fails.
75    pub async fn list_tables(&self, request: &ListTablesRequest) -> Result<ListTablesResponse, AppError> {
76        let db = if request.database_name.is_empty() {
77            None
78        } else {
79            Some(request.database_name.as_str())
80        };
81        let sql = "SELECT tablename FROM pg_tables WHERE schemaname = 'public' ORDER BY tablename";
82        let rows = self.connection.fetch(sql, db).await?;
83        Ok(ListTablesResponse {
84            tables: rows
85                .iter()
86                .filter_map(|r| r.get("tablename").and_then(Value::as_str).map(str::to_owned))
87                .collect(),
88        })
89    }
90}
database_mcp_postgres/tools/list_tables.rs

database_mcp_postgres/tools/
list_tables.rs
