@rsconcept/rstool-mcp

Model Context Protocol adapter for @rsconcept/rstool. Exposes the full RSToolAgent contract — sessions, constituent upserts, RSLang analysis, diagnostics, modeling, evaluation — as MCP tools over stdio, so any MCP-capable host (Cursor, Claude Desktop, your own client) can drive rstool natively.

If you do not need MCP, use @rsconcept/rstool directly (library API or stdio JSON wrapper).

Install

npm install -g @rsconcept/rstool-mcp
# or per-project:
npm install @rsconcept/rstool-mcp

The package ships a rstool-mcp bin that launches the stdio server. It depends on @rsconcept/rstool and (transitively) @rsconcept/domain; no Portal checkout is required.

Run

npx rstool-mcp

The server announces readiness on stderr (rstool-mcp server ready on stdio) and then speaks the MCP protocol on stdin/stdout. There is no HTTP port.

Configure in Cursor

Add the server to your Cursor MCP configuration (~/.cursor/mcp.json):

{
  "mcpServers": {
    "rstool": {
      "command": "npx",
      "args": ["-y", "@rsconcept/rstool-mcp"]
    }
  }
}

Restart Cursor; the tools appear under the rstool server. Pin a version if you prefer reproducible installs:

{
  "mcpServers": {
    "rstool": {
      "command": "npx",
      "args": ["-y", "@rsconcept/[email protected]"]
    }
  }
}

Configure in Claude Desktop

Edit claude_desktop_config.json (~/Library/Application Support/Claude/ on macOS, %APPDATA%\Claude\ on Windows):

{
  "mcpServers": {
    "rstool": {
      "command": "npx",
      "args": ["-y", "@rsconcept/rstool-mcp"]
    }
  }
}

Exposed tools

| MCP tool | Wraps | Notes | |----------|-------|-------| | ping | — | Liveness + contractVersion. | | list_methods | — | Enumerate available tools. | | create_session | RSToolAgent.createSession | Optional initial seed. | | add_or_update_constituenta | addOrUpdateConstituenta | Single upsert. | | analyze_expression | analyzeExpression | Parser + semantic. | | get_form_state | getFormState | Current SessionState. | | list_diagnostics | listDiagnostics | Filterable. | | commit_step | commitStep | Records a SessionRevision. | | export_session | exportSession | JSON string. | | import_session | importSession | Restore from JSON. | | set_constituenta_value | setConstituentaValue | Bind interpretable. | | set_constituenta_values | setConstituentaValues | Batch bindings. | | clear_constituenta_values | clearConstituentaValues | Reset values. | | get_model_state | getModelState | Values + statuses. | | evaluate_expression | evaluateExpression | Scratch evaluation. | | evaluate_constituenta | evaluateConstituenta | Stored derived constituent. | | recalculate_model | recalculateModel | Full recompute. |

Input schemas are intentionally permissive (additionalProperties: true) where the rstool input is structurally rich (e.g. ConstituentaDraft, SessionState); the wrapped RSToolAgent validates inputs at runtime and returns deterministic error responses, surfaced through isError: true on the MCP response.

Programmatic use

If you want to build a custom transport (HTTP, in-process) instead of stdio:

import { StreamableHttpServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js';
import { buildRSToolMcpServer } from '@rsconcept/rstool-mcp';

const server = buildRSToolMcpServer();
const transport = new StreamableHttpServerTransport();
await server.connect(transport);

Or share a single RSToolAgent between multiple servers / requests:

import { RSToolAgent } from '@rsconcept/rstool';
import { buildRSToolMcpServer } from '@rsconcept/rstool-mcp';

const tool = new RSToolAgent();
const server = buildRSToolMcpServer({ tool, name: 'my-rstool-mcp', version: '0.2.0' });

Companion docs

For RS language, the rstool contract, error codes, and common workflows, agents should read @rsconcept/rstool/docs and the bundled rstool-helper skill that ships with @rsconcept/rstool.

Publishing

Maintainers: see PUBLISHING.md for npm release steps.

License

MIT