Your First Query

In this chapter you ask the assistant three questions about your own code and see which mcpls tool answers each one. You will recognize the pattern: you ask in plain language, the assistant picks a tool, and mcpls returns facts from the language server.

Prerequisites

mcpls is connected to your client.
A project that matches an installed language server. Rust needs no further setup; for other languages see Minimal Configuration.

Ask about a type

Open a project and ask:

What is the return type of process_request in src/handlers.rs?

The assistant calls get_hover with the file and the symbol name, and answers from the language server:

You:    What is the return type of process_request in src/handlers.rs?

Claude: [get_hover] It returns Result<Response, ApiError>.
        Response is defined in src/types.rs:23.

The first query after startup can take a few seconds while the language server indexes the project. mcpls waits for indexing to finish (up to 30 seconds by default) rather than answering from a half-built index.

Find every usage

Find everywhere ApiError::Timeout is handled.

Claude: [get_references] Found 4 matches:
        - src/handlers/api.rs:89
        - src/handlers/api.rs:156
        - src/middleware/timeout.rs:34
        - tests/api_tests.rs:201

This is a semantic search: it finds real uses of that variant and skips comments, strings and unrelated names.

Check for errors

Are there compiler errors in src/main.rs?

Claude: [get_diagnostics] 2 errors:
        - line 23: cannot find value `undefined_variable` in this scope
        - line 45: mismatched types: expected `i32`, found `String`

These are the messages the compiler reports, with the line they refer to.

How the assistant addresses code

Tools that point at code take a file_path (an absolute path) and either a position or a symbol name:

line and character, both starting at 1.
symbol_name, such as process_request or Parser::parse, for a symbol defined in that file.

You rarely write these yourself. If a name matches more than one symbol, mcpls reports the candidates instead of guessing, and the assistant retries with a more specific request. Details are in Tools Overview.

What’s Next

See everyday scenarios for prompts that combine these tools into real tasks.

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