Lsp Docs

Requires the agent-lsp MCP server.

lsp-docs

Three-tier documentation lookup for any symbol. Works when the language server is unavailable, when hover returns empty results, or when the symbol lives in a transitive dependency that gopls or pyright does not index.

Read-only — does not modify any files.

Invocation: User provides symbol_name in fully-qualified form (e.g. "fmt.Println", "std::vec::Vec::new", "os.path.join"). Optionally provide file_path for any file in the same module, which improves Go package resolution.

Decision table

Tier 1 — LSP hover (fast, live, position-based)

Call inspect_symbol with the file path and cursor position (1-based).

mcp__lsp__inspect_symbol({
  "file_path": "/abs/path/to/file.go",
  "line": 42,
  "column": 8
})

If the result contains a non-empty contents field with useful type and doc information, stop here and return it. Hover is the fastest path and should always be tried first.

If hover returns empty contents, or the language server is not initialized, proceed to Tier 2.

Tier 2 — Offline toolchain documentation (authoritative, name-based)

Call get_symbol_documentation with the fully-qualified symbol name and language_id. This fetches documentation from the local toolchain (go doc, pydoc, cargo doc) without requiring an LSP session. Works for transitive dependencies that the language server does not index.

mcp__lsp__get_symbol_documentation({
  "symbol": "fmt.Println",
  "language_id": "go",
  "file_path": "/abs/path/to/any/file/in/the/module.go",  // optional, improves Go pkg resolution
  "format": "markdown"   // optional: wraps signature in code fence
})

Interpreting the result:

• If source == "toolchain": return the doc and signature fields to the user. These are authoritative — sourced directly from the installed toolchain, ANSI-stripped, and ready for display.
• If source == "error": note the error field (toolchain failure reason) and proceed to Tier 3.

Tier 3 — Source definition (last resort)

Call go_to_definition to navigate to the symbol definition, then call get_symbol_source to extract the source text. This always works when the symbol exists in the workspace or module cache, even without a language server.

mcp__lsp__go_to_definition({
  "file_path": "/abs/path/to/caller.go",
  "line": 42,
  "column": 8
})
// → returns definition location

mcp__lsp__get_symbol_source({
  "file_path": "<definition file from above>",
  "line": <definition line from above>
})
// → returns full function/type source text

Present the source text to the user with a note that it is raw source, not rendered documentation.

lsp-impact integration note

Before running lsp-impact on an unfamiliar symbol, call get_symbol_documentation to understand its signature and semantics. This prevents misinterpreting the impact report due to incorrect assumptions about what the symbol does.

Example

Goal: look up documentation for http.ListenAndServe in a Go project

Tier 1 — inspect_symbol: cursor on "ListenAndServe" in main.go:14:6
  → contents: "" (empty — server not initialized)
  Proceed to Tier 2.

Tier 2 — get_symbol_documentation:
  symbol: "net/http.ListenAndServe"
  language_id: "go"
  file_path: "/Users/you/code/myapp/main.go"
  format: "markdown"

  Result:
  {
    "symbol": "net/http.ListenAndServe",
    "language": "go",
    "source": "toolchain",
    "doc": "func ListenAndServe(addr string, handler http.Handler) error\n\nListenAndServe listens on the TCP network address addr and then calls Serve...",
    "signature": "func ListenAndServe(addr string, handler http.Handler) error",
    "error": ""
  }

  source == "toolchain" → return doc and signature to user. Done.

Tier 3 — skipped (Tier 2 succeeded)