# `ExAthena.Tools.Lsp`
[🔗](https://github.com/udin-io/ex_athena/blob/v0.7.1/lib/ex_athena/tools/lsp.ex#L1)

Built-in tool that exposes Language Server Protocol queries to the model.

Dispatches four LSP actions — `definition`, `references`, `hover`,
`diagnostics` — by delegating to the running `ExAthena.Lsp.Client` for the
file's language, managed by `ExAthena.Lsp.Manager`.

Before every position-based request the tool sends `textDocument/didOpen`
so the server has an up-to-date buffer. Repeated `didOpen` calls are
tolerated by LSP servers — they re-sync the buffer.

The `diagnostics` action reads push-cached diagnostics
(`textDocument/publishDiagnostics` notifications stored by the client).
It polls every 50 ms up to `@diagnostics_poll_ms` (default 1 500 ms,
overridable via `config :ex_athena, :lsp_diagnostics_poll_ms, ms`).
Servers that only support the LSP 3.17 pull protocol return an empty list —
this is a valid result, not an error.

## Compact schema line

    lsp(action: string, file: string, line?: integer, character?: integer, include_declaration?: boolean) — Query LSP for definition / references / hover / diagnostics.

## Position params

`line` and `character` are **0-indexed** (LSP wire format). The `read`
tool returns 1-indexed line prefixes — subtract 1 before passing here.

## Return shape

`{:ok, formatted_string, ui_payload}` on success.

`formatted_string` per action:
  * `definition` — `path:line:col` entries joined by newline.
  * `references` — count header + one `path:line:col` per line.
  * `hover` — stripped markdown value string.
  * `diagnostics` — `<severity>: <message> at :<line>:<col>` per line,
    or `"count: 0"` when none.

`ui_payload` — `%{kind: :lsp, payload: %{action: atom, file: path, results: list}}`.

## Errors

  * `{:error, :missing_action}` — `"action"` key absent.
  * `{:error, :invalid_action}` — unrecognised action string.
  * `{:error, :missing_file}` — `"file"` key absent.
  * `{:error, :missing_position}` — `line`/`character` absent for position actions.
  * `{:error, :unsupported_language}` — no LSP server for the file's extension.
  * `{:error, {:lsp_error, map}}` — server replied with a JSON-RPC error object.
  * `{:error, :timeout}` — LSP request exceeded the default 30 s timeout.
  * `{:error, {:lsp_port_exit, status}}` — server process died mid-flight.

---

*Consult [api-reference.md](api-reference.md) for complete listing*