dbmcp_sqlite/
handler.rs

1//! `SQLite` handler: composes a [`SqliteConnection`] with the MCP tool router.
2//!
3//! All pool ownership and pool initialization logic lives in the
4//! [`SqliteConnection`]. This module exposes the MCP
5//! `ServerHandler` surface and one thin delegator method that the
6//! per-tool implementations call.
7
8use dbmcp_config::{Config, DatabaseConfig};
9use dbmcp_pii::{Analyzer, Redactor};
10use dbmcp_server::{Server, server_info};
11use rmcp::RoleServer;
12use rmcp::handler::server::router::tool::ToolRouter;
13use rmcp::handler::server::tool::ToolCallContext;
14use rmcp::model::{CallToolRequestParams, CallToolResult, ListToolsResult, PaginatedRequestParams, ServerInfo, Tool};
15use rmcp::service::RequestContext;
16use rmcp::{ErrorData, ServerHandler};
17
18use crate::connection::SqliteConnection;
19use crate::tools::{
20    DropTableTool, ExplainQueryTool, ListTablesTool, ListTriggersTool, ListViewsTool, ReadQueryTool, WriteQueryTool,
21};
22
23/// Backend-specific description for `SQLite`.
24const DESCRIPTION: &str = "Database MCP Server for SQLite";
25
26/// Backend-specific instructions for `SQLite`.
27const INSTRUCTIONS: &str = r"## Workflow
28
291. Call `listTables` to discover tables in the connected database. Pass `search` to filter by name (case-insensitive substring). Pass `detailed: true` to get columns, constraints, indexes, and triggers in the same call — this supersedes the legacy `getTableSchema` workflow.
302. Call `listViews` to discover views in the connected database.
313. Call `listTriggers` to discover triggers in the connected database.
324. Use `readQuery` for read-only SQL (SELECT).
335. Use `writeQuery` for data changes (INSERT, UPDATE, DELETE, CREATE, ALTER, DROP).
346. Use `explainQuery` to analyze query execution plans and diagnose slow queries.
357. Use `dropTable` to remove a table from the database.
36
37## Constraints
38
39- The `writeQuery` and `dropTable` tools are hidden when read-only mode is active.
40- Multi-statement queries are not supported. Send one statement per request.";
41
42/// `SQLite` file-based database handler.
43///
44/// Composes one [`SqliteConnection`] (which owns the pool and
45/// the pool initialization logic) with the per-backend MCP tool router.
46#[derive(Clone)]
47pub struct SqliteHandler {
48    pub(crate) config: DatabaseConfig,
49    pub(crate) connection: SqliteConnection,
50    pub(crate) redactor: Option<Redactor>,
51    tool_router: ToolRouter<Self>,
52}
53
54impl std::fmt::Debug for SqliteHandler {
55    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
56        f.debug_struct("SqliteHandler")
57            .field("read_only", &self.config.read_only)
58            .field("redact_pii", &self.redactor.is_some())
59            .field("connection", &self.connection)
60            .finish_non_exhaustive()
61    }
62}
63
64impl SqliteHandler {
65    /// Creates a new `SQLite` handler.
66    ///
67    /// Constructs the [`SqliteConnection`] (which builds the
68    /// lazy pool) and the MCP tool router. No file I/O happens here.
69    #[must_use]
70    pub fn new(config: &Config) -> Self {
71        Self {
72            config: config.database.clone(),
73            connection: SqliteConnection::new(&config.database),
74            redactor: config
75                .pii
76                .enabled
77                .then(|| Redactor::new(Analyzer::from_pii_config(&config.pii), config.pii.operator.into())),
78            tool_router: build_tool_router(config.database.read_only),
79        }
80    }
81}
82
83impl From<SqliteHandler> for Server {
84    /// Wraps a [`SqliteHandler`] in the type-erased MCP server.
85    fn from(handler: SqliteHandler) -> Self {
86        Self::new(handler)
87    }
88}
89
90/// Builds the tool router, including write tools only when not in read-only mode.
91fn build_tool_router(read_only: bool) -> ToolRouter<SqliteHandler> {
92    let mut router = ToolRouter::new()
93        .with_async_tool::<ListTablesTool>()
94        .with_async_tool::<ListViewsTool>()
95        .with_async_tool::<ListTriggersTool>()
96        .with_async_tool::<ReadQueryTool>()
97        .with_async_tool::<ExplainQueryTool>();
98
99    if !read_only {
100        router = router
101            .with_async_tool::<WriteQueryTool>()
102            .with_async_tool::<DropTableTool>();
103    }
104    router
105}
106
107impl ServerHandler for SqliteHandler {
108    fn get_info(&self) -> ServerInfo {
109        let mut info = server_info();
110        info.server_info.description = Some(DESCRIPTION.into());
111        info.instructions = Some(INSTRUCTIONS.into());
112        info
113    }
114
115    async fn call_tool(
116        &self,
117        request: CallToolRequestParams,
118        context: RequestContext<RoleServer>,
119    ) -> Result<CallToolResult, ErrorData> {
120        let tcc = ToolCallContext::new(self, request, context);
121        self.tool_router.call(tcc).await
122    }
123
124    async fn list_tools(
125        &self,
126        _request: Option<PaginatedRequestParams>,
127        _context: RequestContext<RoleServer>,
128    ) -> Result<ListToolsResult, ErrorData> {
129        Ok(ListToolsResult {
130            tools: self.tool_router.list_all(),
131            next_cursor: None,
132            meta: None,
133        })
134    }
135
136    fn get_tool(&self, name: &str) -> Option<Tool> {
137        self.tool_router.get(name).cloned()
138    }
139}
140
141#[cfg(test)]
142mod tests {
143    use super::*;
144    use dbmcp_config::DatabaseBackend;
145
146    fn handler(read_only: bool) -> SqliteHandler {
147        SqliteHandler::new(&Config {
148            database: DatabaseConfig {
149                backend: DatabaseBackend::Sqlite,
150                name: Some(":memory:".into()),
151                read_only,
152                ..DatabaseConfig::default()
153            },
154            http: None,
155            pii: dbmcp_config::PiiConfig::default(),
156        })
157    }
158
159    #[tokio::test]
160    async fn router_exposes_all_seven_tools_in_read_write_mode() {
161        let router = handler(false).tool_router;
162        for name in [
163            "listTables",
164            "listViews",
165            "listTriggers",
166            "dropTable",
167            "readQuery",
168            "writeQuery",
169            "explainQuery",
170        ] {
171            assert!(router.has_route(name), "missing tool: {name}");
172        }
173    }
174
175    #[tokio::test]
176    async fn router_excludes_get_table_schema() {
177        // Spec 046 US4: `getTableSchema` is retired on SQLite. Both read-only and
178        // read-write catalogues must no longer advertise it.
179        for read_only in [false, true] {
180            let router = handler(read_only).tool_router;
181            assert!(
182                !router.has_route("getTableSchema"),
183                "getTableSchema must be absent (read_only={read_only})"
184            );
185        }
186    }
187
188    #[tokio::test]
189    async fn router_does_not_advertise_backend_specific_tools() {
190        let router = handler(false).tool_router;
191        for absent in [
192            "listDatabases",
193            "listFunctions",
194            "listProcedures",
195            "listMaterializedViews",
196            "createDatabase",
197            "dropDatabase",
198        ] {
199            assert!(!router.has_route(absent), "SQLite must not advertise {absent}");
200        }
201    }
202
203    #[tokio::test]
204    async fn router_hides_write_tools_in_read_only_mode() {
205        let router = handler(true).tool_router;
206        assert!(router.has_route("listTables"));
207        assert!(router.has_route("listViews"));
208        assert!(router.has_route("listTriggers"));
209        assert!(router.has_route("readQuery"));
210        assert!(router.has_route("explainQuery"));
211        assert!(!router.has_route("writeQuery"));
212        assert!(!router.has_route("dropTable"));
213    }
214
215    #[tokio::test]
216    async fn list_tables_annotations() {
217        let router = handler(false).tool_router;
218        let tool = router.get("listTables").expect("listTables registered");
219
220        let annotations = tool.annotations.as_ref().expect("annotations present");
221        assert_eq!(annotations.read_only_hint, Some(true));
222        assert_eq!(annotations.destructive_hint, Some(false));
223        assert_eq!(annotations.idempotent_hint, Some(true));
224        assert_eq!(annotations.open_world_hint, Some(false));
225    }
226}
dbmcp_sqlite/handler.rs

dbmcp_sqlite/
handler.rs
