mcp #

Start the lvkit MCP (Model Context Protocol) server over stdio, so an AI agent can index a VI repo once and then interrogate it like code — project-wide questions answered from a persisted graph, plus deep single-VI inspection on demand.

Synopsis #

lvkit mcp
lvkit mcp --selftest   # initialize + list tools, exit non-zero on failure

mcp takes no arguments beyond -h / --selftest. It runs the same server as the lvkit-mcp console script installed with the lvkit package.

Setup #

The server is stdio — your agent's runtime launches it and speaks to it; you don't run lvkit mcp by hand. With uv installed, no separate lvkit install is needed:

{ "mcpServers": { "lvkit": { "command": "uvx", "args": ["--from", "lvkit", "lvkit-mcp"] } } }

Or, for Claude Code, claude mcp add lvkit -- uvx --from lvkit lvkit-mcp.

Also available one-click, with no config file to write: the Claude Desktop .mcpb, the Claude Code plugin, and the zero-config VS Code extension. For every install path — the one-click bundles, and hand-written config for Claude Code, VS Code, Codex, Copilot CLI, and Cursor — see Installing the MCP server.

Tools #

The server exposes exactly 6 tools, all understanding-only — none of them writes a file. Artifact generation (a Python package, an HTML docs site, a pyvis dependency graph, a diff, an SVG render) is CLI-only (generate, docs, visualize, diff, render): an agent converts a VI by understanding it with read_vi/query and writing idiomatic Python itself — lvkit generate's deterministic AST pipeline is a reference/oracle to verify against, not something the agent calls through MCP.

Project index — whole-repo questions in one call #

index builds a persisted, path-keyed facts index for the enclosing project (so same-named VIs like setUp.vi ×17 never collide); the rest read it in sub-ms. All take a project path (any file/dir inside the repo).

Tool	Description
`index`	Build/refresh the index for a repo (VIs and `.ctl` controls). A full build returns the VI count, `controls`, collisions handled, and ms; `refresh=true` returns `rebuilt`, `deleted`, `total`, `controls` and ms.
`query`	Run one read-only SQL `SELECT`/`WITH` over the index and get back just the answer (a `GROUP BY` histogram, not a row dump). Queries the curated views `vi`, `terminal`, `constant`, `node`, `type_use`, `type`, `type_field`, `type_item`, `vi_used_type`, `typedef`, `typedef_field`, `typedef_ref`, `typedef_use`, `typedef_type`, `class_fact`, `lvproj`.
`query_schema`	List the views and their columns, so a query uses real column names.

Reads of terminals, constants, symbols, and type-uses go through query (e.g. SELECT * FROM terminal WHERE …). node is one row per block-diagram node (a primitive, SubVI call, structure, constant, …) — it's grep for VI code (kind, prim_id, qualified_name, structural parent_uid/frame), not wiring; find a pattern there, then read_vi the matching VI for its actual dataflow.

Call graph and change impact are query over node, not a separate tool. Direct callers of a VI: SELECT DISTINCT vi_path FROM node WHERE callee_path='<abs path>'. Direct callees: SELECT callee_path FROM node WHERE vi_path='<X>' AND kind='vi'. Transitive blast radius: a WITH RECURSIVE over callee_path. vi.callers_count and vi.impact_score are precomputed columns for the counts, so most impact questions don't need the CTE at all. The CLI's callers/callees/blast-radius commands answer the same questions as one-shot commands instead of SQL — there's no MCP tool twin for them; run the SQL above from the agent, or shell out to the CLI command.

The same SQL is available on the CLI as lvkit query.

Deep single-VI — load one VI live, on demand #

Each takes the path of a real .vi — or, for read_ctl and render, a .ctl control — and loads it live (XML already cached) — no load/clear session state.

Tool	Description
`describe`	Human-readable purpose, signature, SubVI calls, control flow.
`read_vi`	The VI as the canonical netlist IR — `{vi, inputs, outputs, components, body}`, faithful type labels, a `kind`-tagged instance/scope body. The structured counterpart to `describe`'s prose.
`read_ctl`	A `.ctl` typedef / custom control as `{typedef, path, kind, type, default, fields, uses}` — the control's own type, enum items, and every field with its recorded default (nested clusters, arrays and saved values included). `render` on the same path draws its front panel.

Resolution gaps — triage before converting #

Tool	Description
`unresolved`	Every unknown primitive / unmapped vi.lib VI under a target (a VI, library, class, or directory), collected in one pass instead of hitting `PrimitiveResolutionNeeded`/`VILibResolutionNeeded` one at a time. Returns a list of `{kind, identifier, name, count, vi_names}` (`kind` is `unknown_primitive` / `unmapped_vilib` / `terminal_mapping`). See SubVI & vi.lib resolution.

Example — the project-understanding demo #

Against JKI VI Tester (487 VIs):

index(project="…/source") → {vis: 487, collisions: 65, ms: …}.
query(project, sql="SELECT name, COUNT(*) AS n FROM terminal WHERE type_descriptor='Error' AND direction='output' GROUP BY name ORDER BY n DESC") → "what does this project call its error indicators?" as a small histogram, in one call. (query builds/refreshes the index on first use, so step 1 is optional.)
query(project, sql="SELECT DISTINCT vi_path FROM node WHERE callee_path='…/fail.vi'") → "does this VI have callers?"
query(project, sql="SELECT name, impact_score FROM vi WHERE path='…/fail.vi'") → "what breaks if I change it?" — the precomputed transitive-dependent count, no CTE needed.

Notes #

The index is project-scoped (keyed by project root) — an agent can work across several repos in one session without a shared global graph to clear.
The index is stored under ~/.lvkit/cache/index/projects/<slug>/index.db (SQLite/WAL), rebuilt cheaply from the content-hash-keyed extraction cache.
Before each call that knows a path, the server re-resolves the project's .lvkit/ store (see setup), so saved primitive/vi.lib mappings apply.
The server runs on both mcp 1.x and 2.0. mcp 2.0 renamed the decorator server FastMCP → MCPServer (moving it from mcp.server.fastmcp to mcp.server.mcpserver) with an otherwise identical API; the server imports whichever the installed SDK ships. --selftest and CI guard against a silent API break on either major.