file snippets for file-content in mcp

Author: DolceTriade

Cargo.toml

@@ -164,7 +164,7 @@ style-file = "public/output.css"
 assets-dir = "public"
 
 # The IP and port (ex: 127.0.0.1:3000) where the server serves the content. Use it in your server setup.
-site-addr = "127.0.0.1:3000"
+site-addr = "0.0.0.0:3000"
 
 # The port to use for automatic reload monitoring
 reload-port = 3001

src/mcp/server.rs

@@ -87,6 +87,7 @@ async fn mcp_docs() -> impl IntoResponse {
             "regex": "Use regex field to enable regex content matching.",
             "path_search_behavior": "path_search requires a non-empty query and is for fuzzy path matching only.",
             "file_list_behavior": "file_list enumerates directories and files with optional recursive depth and limit.",
+            "file_content_behavior": "file_content supports optional start_line/end_line (1-based, inclusive) to return snippets instead of full files.",
             "recency_workflow": "For recent or older change questions: repositories -> repo_branches -> search by branch and compare indexed_at or is_live.",
             "search_fields": [
                 "repo: string",
@@ -116,10 +117,11 @@ async fn mcp_docs() -> impl IntoResponse {
             "5) search({repo, regex:\"pattern\"}) for regex matching",
             "6) file_list(repo, branch, path, depth, limit) for enumeration",
             "7) path_search(repo, branch, query) for fuzzy path lookup",
-            "8) file_content(repo, branch, path) for raw source text",
-            "9) symbol_insights(params) for definitions and references",
-            "10) OR behavior: search({repo, any_terms:[\"termA\",\"termB\"], dedupe:\"repo_path_line\"})",
-            "11) For no results, broaden filters and retry per branch"
+            "8) file_content(repo, branch, path, start_line?, end_line?) for raw source text or snippets",
+            "9) For large files, prefer file_content with line snippets first, then expand only if needed",
+            "10) symbol_insights(params) for definitions and references",
+            "11) OR behavior: search({repo, any_terms:[\"termA\",\"termB\"], dedupe:\"repo_path_line\"})",
+            "12) For no results, broaden filters and retry per branch"
         ]
     }));
     (StatusCode::OK, Json(payload))
@@ -188,7 +190,7 @@ async fn mcp_rpc(Json(req): Json<JsonRpcRequest>) -> Response {
                     "name": "pointer-mcp",
                     "version": env!("CARGO_PKG_VERSION"),
                 },
-                "instructions": "Use tools to query indexed code and symbol information. Operational flow: repositories -> repo_branches -> file_list/path_search -> file_content/search/symbol_insights. Use structured search fields: all_terms are AND semantics and any_terms are OR semantics (fanout + dedupe). For recency/version questions like 'recent change', call repo_branches first, then run search with explicit branch values and compare indexed_at/is_live metadata; add historical:true when historical snapshots should be included. Plain terms do not support wildcard matching; use regex for pattern matching. path_search requires a non-empty query and is not a directory listing endpoint; use file_list for enumeration.",
+                "instructions": "Use tools to query indexed code and symbol information. Operational flow: repositories -> repo_branches -> file_list/path_search -> file_content/search/symbol_insights. Use structured search fields: all_terms are AND semantics and any_terms are OR semantics (fanout + dedupe). For recency/version questions like 'recent change', call repo_branches first, then run search with explicit branch values and compare indexed_at/is_live metadata; add historical:true when historical snapshots should be included. Plain terms do not support wildcard matching; use regex for pattern matching. path_search requires a non-empty query and is not a directory listing endpoint; use file_list for enumeration. For large files, call file_content with start_line/end_line first to limit context size.",
             });
             jsonrpc_result(req.id, result)
         }
@@ -373,13 +375,15 @@ fn mcp_tools() -> Vec<Value> {
         }),
         json!({
             "name": "file_content",
-            "description": "Read raw indexed file content (no syntax highlighting) for an exact repo/branch/path from the index. Use this after file_list/path_search to inspect implementation details. Includes branch freshness metadata.",
+            "description": "Read raw indexed file content (no syntax highlighting) for an exact repo/branch/path from the index. Supports optional start_line/end_line (1-based, inclusive) for snippets to reduce context usage. Use this after file_list/path_search to inspect implementation details. Includes branch freshness metadata.",
             "inputSchema": {
                 "type": "object",
                 "properties": {
                     "repo": { "type": "string" },
                     "branch": { "type": "string" },
-                    "path": { "type": "string" }
+                    "path": { "type": "string" },
+                    "start_line": { "type": "integer", "minimum": 1, "description": "Optional 1-based inclusive start line for snippet responses." },
+                    "end_line": { "type": "integer", "minimum": 1, "description": "Optional 1-based inclusive end line for snippet responses." }
                 },
                 "required": ["repo", "branch", "path"],
                 "additionalProperties": false

src/mcp/tools.rs

@@ -7,11 +7,11 @@ use tokio::time::{Duration, timeout};
 use crate::db::models::{FacetCount, SearchResult, SearchResultsPage};
 use crate::db::{Database, postgres::PostgresDb};
 use crate::mcp::types::{
-    ApiResponse, BranchFreshness, FileContentToolRequest, FileContentToolResponse, FileListEntry,
-    FileListToolRequest, FileListToolResponse, IndexFreshness, PathSearchToolRequest,
-    PathSearchToolResponse, RepoBranchesToolRequest, RepoBranchesToolResponse,
-    RepositoriesToolRequest, RepositoriesToolResponse, SearchCaseMode, SearchDedupeMode,
-    SearchToolRequest, SymbolInsightsToolRequest, SymbolInsightsToolResponse,
+    ApiResponse, BranchFreshness, FileContentSnippet, FileContentToolRequest,
+    FileContentToolResponse, FileListEntry, FileListToolRequest, FileListToolResponse,
+    IndexFreshness, PathSearchToolRequest, PathSearchToolResponse, RepoBranchesToolRequest,
+    RepoBranchesToolResponse, RepositoriesToolRequest, RepositoriesToolResponse, SearchCaseMode,
+    SearchDedupeMode, SearchToolRequest, SymbolInsightsToolRequest, SymbolInsightsToolResponse,
 };
 use crate::pages::file_viewer::{fetch_symbol_insights, search_repo_paths};
 use crate::pages::repo_detail::{RepoBranchDisplay, get_repo_branches};
@@ -84,6 +84,12 @@ pub async fn execute_file_content(
         .map_err(|err| err.to_string())?;
 
     let line_count = raw.content.lines().count();
+    let (content, snippet, returned_line_count) = slice_file_content(
+        &raw.content,
+        payload.start_line,
+        payload.end_line,
+        line_count,
+    )?;
     let index_freshness = resolve_branch_freshness(&payload.repo, &payload.branch, Some(&commit))
         .await
         .unwrap_or_else(|_| unknown_freshness());
@@ -93,12 +99,66 @@ pub async fn execute_file_content(
         commit_sha: raw.commit_sha,
         file_path: raw.file_path,
         language: raw.language,
-        content: raw.content,
+        content,
         line_count,
+        returned_line_count,
+        snippet,
         index_freshness,
     })
 }
 
+fn slice_file_content(
+    content: &str,
+    start_line: Option<u32>,
+    end_line: Option<u32>,
+    total_line_count: usize,
+) -> Result<(String, Option<FileContentSnippet>, usize), String> {
+    if start_line.is_none() && end_line.is_none() {
+        return Ok((content.to_string(), None, total_line_count));
+    }
+
+    let start = start_line.unwrap_or(1);
+    let end = end_line.unwrap_or(total_line_count as u32);
+
+    if start == 0 {
+        return Err("start_line must be >= 1".to_string());
+    }
+    if end == 0 {
+        return Err("end_line must be >= 1".to_string());
+    }
+    if end < start {
+        return Err("end_line must be >= start_line".to_string());
+    }
+    if total_line_count == 0 {
+        return Err("cannot request line snippets from an empty file".to_string());
+    }
+    if start as usize > total_line_count {
+        return Err(format!(
+            "start_line {} exceeds file line count {}",
+            start, total_line_count
+        ));
+    }
+
+    let bounded_end = end.min(total_line_count as u32);
+    let start_idx = (start - 1) as usize;
+    let count = (bounded_end - start + 1) as usize;
+    let snippet_content = content
+        .lines()
+        .skip(start_idx)
+        .take(count)
+        .collect::<Vec<_>>()
+        .join("\n");
+
+    Ok((
+        snippet_content,
+        Some(FileContentSnippet {
+            start_line: start,
+            end_line: bounded_end,
+        }),
+        count,
+    ))
+}
+
 pub async fn execute_file_list(
     payload: FileListToolRequest,
 ) -> Result<FileListToolResponse, String> {
@@ -964,7 +1024,7 @@ fn split_query_tokens(query: &str) -> Vec<String> {
 mod tests {
     use super::{
         build_file_list_entries, build_no_result_guidance, compile_query, normalize_repo_path,
-        quote_if_needed,
+        quote_if_needed, slice_file_content,
     };
 
     #[test]
@@ -1021,4 +1081,33 @@ mod tests {
                 .any(|e| e.kind == "dir" && e.path == "src/mcp")
         );
     }
+
+    #[test]
+    fn slice_file_content_returns_full_content_without_bounds() {
+        let content = "a\nb\nc\n";
+        let (sliced, snippet, returned_line_count) =
+            slice_file_content(content, None, None, 3).expect("slice should succeed");
+        assert_eq!(sliced, content);
+        assert!(snippet.is_none());
+        assert_eq!(returned_line_count, 3);
+    }
+
+    #[test]
+    fn slice_file_content_returns_requested_snippet() {
+        let content = "a\nb\nc\nd";
+        let (sliced, snippet, returned_line_count) =
+            slice_file_content(content, Some(2), Some(3), 4).expect("slice should succeed");
+        assert_eq!(sliced, "b\nc");
+        assert_eq!(returned_line_count, 2);
+        let snippet = snippet.expect("snippet metadata must be present");
+        assert_eq!(snippet.start_line, 2);
+        assert_eq!(snippet.end_line, 3);
+    }
+
+    #[test]
+    fn slice_file_content_rejects_invalid_bounds() {
+        let content = "a\nb\nc";
+        let err = slice_file_content(content, Some(4), None, 3).expect_err("must reject");
+        assert!(err.contains("exceeds file line count"));
+    }
 }

src/mcp/types.rs

@@ -135,6 +135,10 @@ pub struct FileContentToolRequest {
     pub repo: String,
     pub branch: String,
     pub path: String,
+    #[serde(default)]
+    pub start_line: Option<u32>,
+    #[serde(default)]
+    pub end_line: Option<u32>,
 }
 
 #[derive(Debug, Deserialize)]
@@ -171,9 +175,18 @@ pub struct FileContentToolResponse {
     pub language: Option<String>,
     pub content: String,
     pub line_count: usize,
+    pub returned_line_count: usize,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub snippet: Option<FileContentSnippet>,
     pub index_freshness: IndexFreshness,
 }
 
+#[derive(Debug, Serialize)]
+pub struct FileContentSnippet {
+    pub start_line: u32,
+    pub end_line: u32,
+}
+
 #[derive(Debug, Deserialize)]
 pub struct FileListToolRequest {
     pub repo: String,