Prequisites - Spec Driven Design

Overview
Prerequisites

Overview

For more information about Spec Driven Design (SDD), see:

Prerequisites

The following prerequisites are required:

A vFunction Application with a Baseline Measurement
The vFunction MCP server connected to your Coding Agent
The Skills Installed
The Codebase Available Locally

A vFunction Application with a Baseline Measurement

Spec Driven Design (SDD) Pipeline Agent Skills 1 and 2 read the platform’s runtime analysis: domains, entry points, call trees, and architectural TODOs. Domains cannot be fetched until a baseline measurement is set.

The vFunction MCP Server Connected to your Coding Agent

The application must be selected in your workspace configuration. Every tool call resolves the application from that configuration.

The Skills Installed

The skills ship with the vFunction server, separately from the MCP tool surface. The local MCP CLI installs them for you. From the root of the project you are working in:

vf_mcp login             # browser OAuth2; credentials go to the OS keychain (once per machine)
vf_mcp workspace         # creates .vfunction/vf-mcps.json for this project, if not already present
vf_mcp ping              # confirms authentication and server connectivity
vf_mcp download-skill    # downloads and installs the skills

Note that the download-skill command installs every skill in the archive into both of these locations, relative to the current directory:

.claude/skills/<skill-name>/     # Claude Code
.kiro/skills/<skill-name>/       # Kiro

Run the command again to update. Each skill folder is deleted and rewritten, so a file removed between versions does not linger. Reload the agent afterwards if the new skills do not appear. Each folder contains a SKILL.md that the agent reads automatically; you never need to open these files yourself.

Some additional notes:

The install is per project, into the working directory and not into ~. A new checkout needs download-skill run again.
The archive endpoint (GET /api/v1/mcp/skills/archive) requires an authenticated browser session, so fetching it with curl will not work. Use download-skill, or download the archive from a logged-in browser.

The Codebase Available Locally

Spec Driven Design (SDD) Pipeline Agent Skills 1 and 2, and (optionally) 3 read the source.

Choosing a specs directory

We recommend keeping specs outside the codebase project, for example ../specs/. When multiple agents extract different domains in parallel, none of them can then read the output of the others. The examples in this guide use ../specs/.

Kiro users

Kiro restricts access to directories outside the project it is working in, which can cause repeated permission problems during a run. When using Kiro, use a sub-directory inside the project instead, such as ./specs/. Claude Code has no such restriction.