# Update MCP > Create, update, or manage universal-ai-config MCP server templates. Handles finding existing configs, deciding whether to create or modify, and writing the template. Use when this capability is needed. - Skill: `tomevault-io/update-mcp` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/update-mcp` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/update-mcp/raw - Safety review: pending (external: skill-scanner PASS, skillspector PASS) - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: AI & ML - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/update-mcp --- # Manage MCP Server Templates MCP (Model Context Protocol) server configurations define external tool servers available to AI tools. They use JSON format (not markdown), similar to hooks. ## Finding Existing MCP Configs List files in `<%= mcpTemplatePath() %>/` to discover existing MCP templates (`.json` files). Read them to understand what servers are already configured. **Note:** Servers from multiple files are merged by server name during generation (last-wins for duplicates). You can organize servers by concern (e.g. `github.json`, `databases.json`). ## Additional Template Directories This project may have additional template directories configured via `additionalTemplateDirs`. To find them, search the project root for **all** config files matching `universal-ai-config.*` (e.g. `universal-ai-config.config.ts`, `universal-ai-config.overrides.config.ts`, and any other variants) and read the `additionalTemplateDirs` field from each. If the user asks to update a template that doesn't exist in the main templates directory, or explicitly refers to shared/global/external templates: 1. Read all `universal-ai-config.*` config files in the project root to find `additionalTemplateDirs` paths 2. Search those directories for the relevant MCP config 3. **IMPORTANT:** Before editing any file outside the main `<%= config.templatesDir %>/` directory, ask the user for explicit confirmation — these are shared templates that may affect other projects ## Deciding What to Do - **Create new file**: for an entirely new server or group of related servers - **Update existing file**: modify server config, add servers to an existing file - **Merge strategy**: since servers merge by name, you can split them across files for better organization - **Delete**: remove an MCP config file when the server is no longer needed ## Creating a New MCP Config 1. Create a `.json` file in `<%= mcpTemplatePath() %>/` with a descriptive name (e.g. `github.json`) 2. Use the standard MCP JSON structure ### JSON Structure ```json { "mcpServers": { "server-name": { "type": "stdio", "command": "npx", "args": ["-y", "@some/mcp-server"], "env": { "API_KEY": "${API_KEY}" } } } } ``` ### Server Fields | Field | Type | Description | | --------- | ------------------------ | -------------------------------------------------- | | `type` | `string` | Transport type (`"stdio"` or `"sse"`) | | `command` | `string` | Command to launch the server (for stdio transport) | | `args` | `string[]` | Arguments for the command | | `env` | `Record` | Environment variables | | `url` | `string` | Server URL (for SSE/HTTP transport) | | `headers` | `Record` | HTTP headers (for SSE/HTTP transport) | A server must have either `command` (stdio) or `url` (SSE/HTTP). If neither is present after per-target override resolution, the server is dropped for that target. ### Variable Interpolation Use `{{variableName}}` syntax to reference variables from the config file. Variables support **typed resolution**: when the entire JSON value is `"{{varName}}"`, it resolves to the raw typed value (array, object, number, boolean). When embedded in other text, it does string interpolation. ```json { "mcpServers": { "playwright": { "command": "npx", "args": "{{playwrightArgs}}", "env": { "API_HOST": "{{apiHost}}" } } } } ``` Variables are defined in `universal-ai-config.config.ts`: ```typescript export default defineConfig({ variables: { playwrightArgs: ['-y', '@playwright/mcp@latest'], apiHost: 'api.example.com', }, }) ``` For environment-specific values, use `universal-ai-config.overrides.ts` (gitignored): ```typescript export default defineConfig({ variables: { playwrightArgs: [ '-y', '@playwright/mcp@latest', '--headless', '--executable-path', '/opt/google/chrome/chrome', ], }, }) ``` **Important:** `{{varName}}` is for uac config variables. Use `${ENV_VAR}` for runtime environment variable references that should be passed through to the generated output unchanged. ### Per-Target Overrides Any server field can have per-target values using the same override syntax as hooks: ```json { "mcpServers": { "my-server": { "command": { "default": "npx", "cursor": "node" }, "args": { "default": ["-y", "@my/server"], "cursor": ["./mcp-server.js"] }, "type": { "claude": "stdio", "copilot": "stdio" } } } } ``` If `command` (and `url`) resolve to `undefined` for a target, the entire server is dropped for that target. This lets you define target-exclusive servers. ### Copilot Inputs For Copilot, you can include an `inputs` array for interactive secret prompts: ```json { "mcpServers": { "github": { "command": "npx", "args": ["-y", "@modelcontextprotocol/server-github"], "env": { "GITHUB_TOKEN": "${input:github-token}" } } }, "inputs": [ { "type": "promptString", "id": "github-token", "description": "GitHub Personal Access Token", "password": true } ] } ``` The `inputs` array is only included in Copilot output — Claude and Cursor ignore it. ### Output Paths Generated MCP files are placed at root-relative paths (not inside the target's output directory): | Target | Output Path | Wrapper Key | | ------- | ------------------ | ------------ | | Claude | `.mcp.json` | `mcpServers` | | Copilot | `.vscode/mcp.json` | `servers` | | Cursor | `.cursor/mcp.json` | `mcpServers` | **Note:** Cursor omits the `type` field from generated output (it infers transport from the presence of `command` vs `url`). ### Example ```json { "mcpServers": { "github": { "type": "stdio", "command": "npx", "args": ["-y", "@modelcontextprotocol/server-github"], "env": { "GITHUB_TOKEN": "${GITHUB_TOKEN}" } }, "postgres": { "type": "stdio", "command": "npx", "args": ["-y", "@modelcontextprotocol/server-postgres", "{{dbConnectionString}}"] } } } ``` ## After Changes Run `uac generate` to regenerate target-specific config files and verify the output. **Reminder:** Always edit templates in `<%= mcpTemplatePath() %>/` — never edit generated MCP files (`.mcp.json`, `.vscode/mcp.json`, `.cursor/mcp.json`) directly. --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/fabis94) — claim your Tome and manage your conversions.