@askturret/mcp-explorer

Local, dev-only Explorer UI — a Swagger-like human view of the effective MCP tool surface, with a safe test-invoke panel.

It renders from the same RegistrySnapshot the transport serves, so what it shows cannot drift from what tools/list returns, and it invokes tools through the same /mcp endpoint any MCP client uses. There is no Explorer-private endpoint.

What it shows

• Every visible tool in the current snapshot, filterable.
• Per-tool detail: description, input and output schema as a JSON Schema tree with per-field docs, effect flags, and executor type.
• A test-invoke form derived from the input schema, submitted as tools/call.
• A response viewer showing the pretty-printed result or the typed error.
• Registry hash, version and createdAt in the header.

Usage from an adapter

import { buildExplorerViewModel, renderExplorerHtml } from '@askturret/mcp-explorer';

const html = renderExplorerHtml(buildExplorerViewModel(registry.current(), basePath));

buildExplorerViewModel is pure — snapshot in, view model out — so an adapter only has to serve the string. The Express adapter mounts it at ${basePath}/explorer.

Diagnostic panels (#56)

renderExplorerHtml takes an optional second argument — the six diagnostic panels from buildExplorerPanels:

const html = renderExplorerHtml(model, buildExplorerPanels({ /* live state */ }));

Omit it and the page is unchanged apart from per-tool provenance, which rides on the view model and needs nothing from the host. Adapters expose this as the explorerPanels option, called per request. See docs/explorer-panels.md.

Everything embedded in the page is redacted at serialization, so a hand-built panel set cannot route around the pipeline the builders apply.

Production

Per §10.1 invariant 9, the Explorer is disabled by default when NODE_ENV=production, where the route returns 404. An operator can opt in explicitly (enableExplorer: true), which is not blocked but logs a startup warning naming the setting.

Enabling it in production is risky and deliberately so: the Explorer publishes the full tool surface and can invoke tools. It has no authentication of its own — it inherits only whatever the host app puts in front of ${basePath}/explorer. Protecting that route is the adopter's responsibility.

Executor config is never sent to the browser; only the executor type is, since config can hold upstream URLs and credential references.

Delivery

A single self-contained HTML document with inline CSS and JS — no framework, no build step, no runtime dependency. A typical page is ~5 KB gzipped, against the 100 KB budget in the architecture doc.

Scope

This is the v0.1 developer inner-loop. Provenance UI, policy explanation, trace/audit history, breaker/bulkhead state, version diff and the principal-aware effective surface ship with their owning epics.