Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add commands/paiml/rust-mcp-sdk/previewgit clone --depth 1 https://github.com/paiml/rust-mcp-sdkWhat it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00000 | $0.00396 |
| Opus 5 | $0.00000 | $0.00198 |
| Sonnet 5 | $0.00000 | $0.00079 |
| Haiku 4.5 | $0.00000 | $0.00040 |
Grade A, and why
preview scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
What it actually says
cargo pmcp preview
Preview MCP Apps widgets in a browser.
Usage
cargo pmcp preview --url <URL> [OPTIONS]
Description
Launches a browser-based preview environment for testing MCP servers that return widget UI. Simulates the ChatGPT Apps runtime with dual proxy/WASM bridge modes.
When --widgets-dir is set, widget HTML files are read directly from disk on each request, enabling hot-reload during development (just refresh the browser).
Options
| Option | Default | Description |
|---|---|---|
--url <URL> |
(required) | URL of the running MCP server |
--port <PORT> |
8765 |
Port for the preview server |
--open |
- | Open browser automatically |
--tool <TOOL> |
- | Auto-select this tool on start |
--theme <THEME> |
light |
Initial theme (light or dark) |
--locale <LOCALE> |
en-US |
Initial locale |
--widgets-dir <DIR> |
- | Path to widgets directory for file-based authoring (hot-reload) |
Examples
Basic preview with auto-open:
cargo pmcp preview --url http://localhost:3000 --open
File-based widget authoring with hot-reload:
cargo pmcp preview --url http://localhost:3000 --widgets-dir ./widgets --open
Dark theme, auto-select a specific tool:
cargo pmcp preview --url http://localhost:3000 --theme dark --tool chess_board
Related Commands
cargo pmcp app- Scaffold and manage MCP Apps projectscargo pmcp dev- Start the MCP server before previewing
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 3d ago First seen · 50 lines · 0 tokens per session scan A 919f57001257
preview is a command published in the GitHub repository paiml/rust-mcp-sdk (53 stars, last pushed 3d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 396 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other commands, from other repositories
auto-browse
Auto-browse — learn, optimize, and graduate browser operations or web data-mining workflows.
cli-anything-web:refine
Refine an existing cli-anything-web CLI by recording additional traffic and expanding command coverage. Invokes the gap-analyzer skill as its first step, then implements missing endpoints.
connect
Connect to OpenChrome and confirm the MCP server is reachable. Runs a quick health check, reports the Chrome CDP status, and prints the tool surface summary.
check-access
Check whether a user or group can access a specific URL via ZIA policies.
findmy
Look up Find My friend locations on macOS (name, location, staleness, distance) via Vision OCR of FindMy.app.
browser
Debug and fix browser issues by inspecting, diagnosing, and resolving visual or technical problems.