lean_ctx/server/
tool_trait.rs

1use rmcp::model::Tool;
2use rmcp::ErrorData;
3use serde_json::{Map, Value};
4
5/// Result returned by an McpTool handler.
6pub struct ToolOutput {
7    pub text: String,
8    pub original_tokens: usize,
9    pub saved_tokens: usize,
10    pub mode: Option<String>,
11    /// Path associated with the tool call (for record_call_with_path).
12    pub path: Option<String>,
13    /// True when the tool mutated state that clients should know about
14    /// (e.g. dynamic tool categories changed).
15    pub changed: bool,
16}
17
18impl ToolOutput {
19    pub fn simple(text: String) -> Self {
20        Self {
21            text,
22            original_tokens: 0,
23            saved_tokens: 0,
24            mode: None,
25            path: None,
26            changed: false,
27        }
28    }
29
30    /// Compact one-line summary for headers_only response verbosity.
31    pub fn to_header_line(&self, tool_name: &str) -> String {
32        let path_str = self.path.as_deref().unwrap_or("—");
33        let mode_str = self.mode.as_deref().unwrap_or("—");
34        let sent = self.original_tokens.saturating_sub(self.saved_tokens);
35        let pct = if self.original_tokens > 0 {
36            (self.saved_tokens as f64 / self.original_tokens as f64 * 100.0) as u32
37        } else {
38            0
39        };
40        format!("[{tool_name}: {path_str}, mode={mode_str}, {sent} tok sent, -{pct}%]")
41    }
42
43    pub fn with_savings(text: String, original: usize, saved: usize) -> Self {
44        Self {
45            text,
46            original_tokens: original,
47            saved_tokens: saved,
48            mode: None,
49            path: None,
50            changed: false,
51        }
52    }
53}
54
55/// Trait for a self-contained MCP tool. Each tool provides its own schema
56/// definition and handler, eliminating the possibility of schema/handler drift.
57///
58/// This trait is the plugin interface for LcpTools: any implementation can be
59/// registered at runtime via `ToolRegistry::register()`. Future plugin system
60/// will load implementations from shared libraries or subprocess bridges.
61///
62/// Handlers are synchronous because all existing tool handlers are sync.
63/// The async boundary (cache locks, session reads) is handled by the dispatch
64/// layer before calling `handle`.
65pub trait McpTool: Send + Sync {
66    /// Tool name as registered in the MCP protocol (e.g. "ctx_tree").
67    fn name(&self) -> &'static str;
68
69    /// MCP tool definition including JSON schema. This replaces the
70    /// corresponding entry in `granular_tool_defs()`.
71    fn tool_def(&self) -> Tool;
72
73    /// Execute the tool. Args are the raw JSON-RPC arguments.
74    /// `ctx` provides access to resolved paths and project state.
75    fn handle(&self, args: &Map<String, Value>, ctx: &ToolContext)
76        -> Result<ToolOutput, ErrorData>;
77}
78
79/// Context passed to tool handlers. Contains pre-resolved values that
80/// many tools need, avoiding repeated async lock acquisition inside
81/// handlers. Extended with shared server state for tools that need
82/// cache/session access.
83pub struct ToolContext {
84    pub project_root: String,
85    pub minimal: bool,
86    /// Pre-resolved paths keyed by argument name (e.g. "path" -> "/abs/dir").
87    pub resolved_paths: std::collections::HashMap<String, String>,
88    /// CRP mode for compression-aware tools.
89    pub crp_mode: crate::tools::CrpMode,
90    /// Shared cache handle for tools that need read/write access.
91    pub cache: Option<crate::tools::SharedCache>,
92    /// Shared session handle for tools that need session access.
93    pub session: Option<std::sync::Arc<tokio::sync::RwLock<crate::core::session::SessionState>>>,
94    /// Tool call records for session-aware tools (e.g. ctx_session status).
95    pub tool_calls:
96        Option<std::sync::Arc<tokio::sync::RwLock<Vec<crate::core::protocol::ToolCallRecord>>>>,
97    /// Current agent identity for multi-agent tools.
98    pub agent_id: Option<std::sync::Arc<tokio::sync::RwLock<Option<String>>>>,
99    /// Active workflow run state.
100    pub workflow:
101        Option<std::sync::Arc<tokio::sync::RwLock<Option<crate::core::workflow::WorkflowRun>>>>,
102    /// Context ledger for handoff operations.
103    pub ledger:
104        Option<std::sync::Arc<tokio::sync::RwLock<crate::core::context_ledger::ContextLedger>>>,
105    /// Client name (cursor, claude, etc.).
106    pub client_name: Option<std::sync::Arc<tokio::sync::RwLock<String>>>,
107    /// Pipeline stats for metrics/proof tools.
108    pub pipeline_stats:
109        Option<std::sync::Arc<tokio::sync::RwLock<crate::core::pipeline::PipelineStats>>>,
110    /// Global call counter for context tools.
111    pub call_count: Option<std::sync::Arc<std::sync::atomic::AtomicUsize>>,
112    /// Autonomy state for search repeat detection.
113    pub autonomy: Option<std::sync::Arc<crate::tools::autonomy::AutonomyState>>,
114    /// Pre-computed context pressure snapshot for synchronous gate decisions.
115    pub pressure_snapshot: Option<crate::core::context_ledger::ContextPressure>,
116    /// Errors from path resolution (PathJail rejection, secret path, etc.).
117    /// Keyed by argument name (e.g. "path" -> "path escapes project root: ...").
118    pub path_errors: std::collections::HashMap<String, String>,
119}
120
121impl ToolContext {
122    pub fn resolved_path(&self, arg: &str) -> Option<&str> {
123        self.resolved_paths.get(arg).map(String::as_str)
124    }
125
126    /// Returns the path resolution error for a given key, if any.
127    pub fn path_error(&self, key: &str) -> Option<&str> {
128        self.path_errors.get(key).map(String::as_str)
129    }
130
131    /// Sync path resolution using project_root. Simplified version
132    /// of LeanCtxServer::resolve_path for use in sync tool handlers.
133    pub fn resolve_path_sync(&self, path: &str) -> Result<String, String> {
134        let normalized = crate::core::pathutil::normalize_tool_path(path);
135        if normalized.is_empty() || normalized == "." {
136            return Ok(normalized);
137        }
138        let p = std::path::Path::new(&normalized);
139        let resolved = if p.is_absolute() || p.exists() {
140            std::path::PathBuf::from(&normalized)
141        } else {
142            let joined = std::path::Path::new(&self.project_root).join(&normalized);
143            if joined.exists() {
144                joined
145            } else {
146                std::path::Path::new(&self.project_root).join(&normalized)
147            }
148        };
149        let jail_root = std::path::Path::new(&self.project_root);
150        let jailed = crate::core::pathjail::jail_path(&resolved, jail_root)?;
151        crate::core::io_boundary::check_secret_path_for_tool("resolve_path", &jailed)?;
152        Ok(crate::core::pathutil::normalize_tool_path(
153            &jailed.to_string_lossy().replace('\\', "/"),
154        ))
155    }
156}
157
158// ── Arg extraction helpers (mirror server/helpers.rs for standalone use) ──
159
160/// Extract a resolved path from context with differentiated error messages.
161/// Returns descriptive errors for: missing param, PathJail rejection, wrong type.
162pub fn require_resolved_path(
163    ctx: &ToolContext,
164    args: &Map<String, Value>,
165    key: &str,
166) -> Result<String, ErrorData> {
167    if let Some(path) = ctx.resolved_path(key) {
168        return Ok(path.to_string());
169    }
170    if let Some(err) = ctx.path_error(key) {
171        return Err(ErrorData::invalid_params(format!("{key}: {err}"), None));
172    }
173    if let Some(val) = args.get(key) {
174        if !val.is_string() {
175            let type_name = match val {
176                Value::Number(_) => "number",
177                Value::Bool(_) => "boolean",
178                Value::Array(_) => "array",
179                Value::Object(_) => "object",
180                Value::Null => "null",
181                Value::String(_) => unreachable!(),
182            };
183            return Err(ErrorData::invalid_params(
184                format!("{key} must be a string, got {type_name}"),
185                None,
186            ));
187        }
188    }
189    Err(ErrorData::invalid_params(
190        format!("{key} is required"),
191        None,
192    ))
193}
194
195pub fn get_str(args: &Map<String, Value>, key: &str) -> Option<String> {
196    args.get(key).and_then(|v| v.as_str()).map(String::from)
197}
198
199pub fn get_int(args: &Map<String, Value>, key: &str) -> Option<i64> {
200    args.get(key).and_then(serde_json::Value::as_i64)
201}
202
203pub fn get_bool(args: &Map<String, Value>, key: &str) -> Option<bool> {
204    args.get(key).and_then(serde_json::Value::as_bool)
205}
206
207pub fn get_str_array(args: &Map<String, Value>, key: &str) -> Option<Vec<String>> {
208    args.get(key).and_then(|v| v.as_array()).map(|arr| {
209        arr.iter()
210            .filter_map(|v| v.as_str().map(String::from))
211            .collect()
212    })
213}
214
215#[cfg(test)]
216mod tests {
217    use super::*;
218    use serde_json::json;
219
220    fn empty_ctx() -> ToolContext {
221        ToolContext {
222            project_root: String::new(),
223            minimal: false,
224            resolved_paths: std::collections::HashMap::new(),
225            crp_mode: crate::tools::CrpMode::Off,
226            cache: None,
227            session: None,
228            tool_calls: None,
229            agent_id: None,
230            workflow: None,
231            ledger: None,
232            client_name: None,
233            pipeline_stats: None,
234            call_count: None,
235            autonomy: None,
236            pressure_snapshot: None,
237            path_errors: std::collections::HashMap::new(),
238        }
239    }
240
241    #[test]
242    fn require_resolved_path_returns_resolved() {
243        let mut ctx = empty_ctx();
244        ctx.resolved_paths
245            .insert("path".to_string(), "/abs/file.rs".to_string());
246        let args: Map<String, Value> = Map::new();
247        let result = require_resolved_path(&ctx, &args, "path");
248        assert_eq!(result.unwrap(), "/abs/file.rs");
249    }
250
251    #[test]
252    fn require_resolved_path_surfaces_jail_error() {
253        let mut ctx = empty_ctx();
254        ctx.path_errors.insert(
255            "path".to_string(),
256            "path escapes project root /project".to_string(),
257        );
258        let args: Map<String, Value> = Map::new();
259        let result = require_resolved_path(&ctx, &args, "path");
260        assert!(result.is_err());
261        let err = result.unwrap_err();
262        let msg = format!("{err:?}");
263        assert!(msg.contains("escapes project root"), "got: {msg}");
264    }
265
266    #[test]
267    fn require_resolved_path_detects_non_string() {
268        let ctx = empty_ctx();
269        let mut args: Map<String, Value> = Map::new();
270        args.insert("path".to_string(), json!(42));
271        let result = require_resolved_path(&ctx, &args, "path");
272        assert!(result.is_err());
273        let err = result.unwrap_err();
274        let msg = format!("{err:?}");
275        assert!(msg.contains("must be a string, got number"), "got: {msg}");
276    }
277
278    #[test]
279    fn require_resolved_path_missing_param() {
280        let ctx = empty_ctx();
281        let args: Map<String, Value> = Map::new();
282        let result = require_resolved_path(&ctx, &args, "path");
283        assert!(result.is_err());
284        let err = result.unwrap_err();
285        let msg = format!("{err:?}");
286        assert!(msg.contains("path is required"), "got: {msg}");
287    }
288}
lean_ctx/server/tool_trait.rs

lean_ctx/server/
tool_trait.rs
