Code Intelligence

In this chapter you learn the tools for reading code: types, definitions, usages, outlines and completions. They answer “what is this, where does it come from, and who uses it”. Addressing and result flags are explained in Tools Overview.

Prerequisites

You know how to address code.

get_hover

Returns the type signature and documentation for the symbol at a position.

Arguments: file_path, and line with character or symbol_name (with optional symbol_kind, container).

{ "file_path": "/work/app/src/models.rs", "line": 10, "character": 5 }

{
  "contents": "```rust\nstruct User {\n    id: u64,\n    name: String,\n}\n```\n\nUser information structure.",
  "range": {
    "start": { "line": 10, "character": 5 },
    "end": { "line": 10, "character": 9 }
  }
}

The result is null when the server has no hover information for that position. Hover works best with statically typed languages.

get_definition

Returns where a symbol is defined, across files and crates.

Arguments: the same addressing as get_hover, plus optional context (see enclosing-symbol context).

{ "file_path": "/work/app/src/billing.rs", "symbol_name": "process_payment" }

[
  {
    "uri": "file:///work/app/src/billing.rs",
    "range": {
      "start": { "line": 23, "character": 0 },
      "end": { "line": 23, "character": 14 }
    },
    "out_of_workspace": false
  }
]

A symbol with several definitions returns several locations; an unknown symbol returns an empty array.

get_references

Finds every usage of a symbol in the workspace.

Arguments: addressing as above, plus include_declaration (default false) and optional context.

{
  "file_path": "/work/app/src/errors.rs",
  "symbol_name": "Timeout",
  "container": "ApiError",
  "context": "enclosing_symbol"
}

Each location has uri, range, out_of_workspace and, with context, the enclosing_symbol. Searching a very common symbol can be slow, and the list is capped (truncated: true).

get_document_symbols

Returns the outline of one file as a hierarchy of symbols (types, functions, fields) with their ranges.

{ "file_path": "/work/app/src/models.rs" }

Use it to understand a file before reading it, or to find the exact name for a symbol_name argument. Each symbol has a numeric kind such as 5 (class or struct), 6 (method), 8 (field), 11 (interface or trait) and 12 (function).

workspace_symbol_search

Searches symbol names across the whole workspace, with partial and fuzzy matching. It needs no file, so it is the way in when you only know a name.

Arguments: query (required), limit (default 100, capped by the server) and kind_filter (a kind name such as function or class, or the numeric LSP kind).

{ "query": "SessionManager", "kind_filter": "struct" }

This tool has no document to route on. mcpls sends it to the first server that explicitly claims workspace_symbols in handles, otherwise to the first catch-all server.

get_document_highlights

Lists the occurrences of the symbol at a position inside the same file, each marked read, write or text. It is the file-local subset of get_references and is faster.

{ "file_path": "/work/app/src/billing.rs", "line": 42, "character": 9 }

get_signature_help

Returns the signatures and parameter documentation for the call at a position, with the active signature and parameter. Position it inside the parentheses of a call.

{ "file_path": "/work/app/src/billing.rs", "line": 57, "character": 31 }

get_completions

Returns completion candidates at a position. Add trigger (for example ., : or ->) to mimic typing a trigger character.

{ "file_path": "/work/app/src/billing.rs", "line": 57, "character": 18, "trigger": "." }

Each item has a label, a numeric kind (2 method, 3 function, 5 field, 6 variable, 7 class, 9 module), a detail, optional documentation and insertText. Completion requests are capped at 10 seconds whatever request_timeout_seconds says.

get_inlay_hints

Returns the inferred type and parameter-name annotations an editor would draw inline, for a range.

{
  "file_path": "/work/app/src/billing.rs",
  "start_line": 40, "start_character": 1,
  "end_line": 60, "end_character": 1
}

Use it to see inferred types of let bindings without hovering over each one.

What’s Next

Continue with Diagnostics and Formatting to see what the compiler reports.

Keyboard shortcuts

mcpls