Railway's official agent skill: create projects, provision databases and buckets, deploy, manage variables and domains, and read build failures back — from the CLI, API or MCP server.
MCP Apps Tool and Widget GeneratorSkill
Summary
Microsoft's official plugin that generates codeful MCP tools — a self-contained JS runtime plus JSON Schema metadata — and single-file HTML widgets to visualise their results.
Features
- Generates a self-contained runTool() JavaScript runtime with no external dependencies
- Emits a JSON sidecar with MCP annotations, input schema and structured output schema
- Types Dataverse-backed tools against real table schemas discovered via PAC CLI
- Builds single-file HTML widgets that embed their runtime for restrictive hosts
- Optional CDN mode for widgets, opt-in only
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Description
The official Microsoft plugin for building MCP Apps: codeful Model Context Protocol tools paired with interactive widgets that render their output. It is a narrow, unusually well-specified generator, and the constraints it enforces are the interesting part.
`/generate-codeful-mcp-tool` produces a matched pair from a description of the tool's purpose, inputs, expected result and any Dataverse data it needs:
<tool-name>.tool.js— a self-contained runtime exportingrunTool({ toolInput, dataApi }), with no packages, imports, network access, filesystem access, environment variables or persistent state.<tool-name>.tool.json— registration metadata: name, description, MCP behaviour annotations (such asreadOnlyHint), input schema and structured output schema.
Keeping registration in a JSON sidecar rather than in executable code is a deliberate separation that makes tools reviewable. For Dataverse-backed tools the skill uses the PAC CLI to discover exact table logical names and generates a temporary RuntimeTypes.ts carrying verified columns, lookup shapes and choice values, deleting it after generation — so the emitted code is typed against the real schema rather than a guess.
`/generate-mcp-app-ui` creates a single-file HTML widget that visualises a tool's result. By default it embeds its runtime inline, so it works on hosts that block public URLs; a CDN mode is available but must be opted into explicitly. Widgets can consume model-visible content, structured output and widget-private metadata, and are built with Fluent UI.
Published by Microsoft under the MIT licence for Claude Code and GitHub Copilot CLI.
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