instill

instill

A Go library for installing Agent Skills into AI coding agents and detecting which agent is running your code.

40 agents can't agree on where to put a markdown file or which env var to set. instill deals with it so you don't have to.

your-tool/
└── skills/
    └── your-skill/
        ├── SKILL.md              # instructions + frontmatter
        └── references/           # optional detailed docs
            └── commands.md

No SDK, no runtime, no protocol. Markdown files in the right directories. Env vars in the right if statements.

Looking for a standalone tool to manage skills? Use vercel-labs/skills instead. instill is a Go library for CLI tools that want to bundle and install their own agent skills as part of their distribution.

Install skills

import (
    "embed"
    "fmt"
    "log"

    "github.com/tiulpin/instill"
)

//go:embed skills
var skills embed.FS

func main() {
    // Detect which agents are present
    agents, _ := instill.Detect(".", false)
    names := make([]string, len(agents))
    for i, a := range agents {
        names[i] = a.Name
    }

    // Install skill files to each agent's expected location
    results, err := instill.Install(skills, instill.Options{
        Agents:     names,
        ProjectDir: ".",
    })
    if err != nil {
        log.Fatal(err)
    }
    for _, r := range results {
        fmt.Printf("%s: %s (existed=%v)\n", r.Agent, r.Path, r.Existed)
    }
}

Detect the running agent

if agent := instill.DetectRuntime(); agent != nil {
    fmt.Printf("running inside %s (detected via %s)\n", agent.DisplayName, agent.EnvVar)
    // → "running inside Claude Code (detected via CLAUDECODE)"
}

Detection priority:

1. AI_AGENT — the emerging universal standard that everyone will adopt any day now
2. AGENT — used by Amp, Goose
3. CLAUDE_CODE_IS_COWORK — Claude Code cowork sessions
4. Agent-specific env vars (CLAUDECODE, CURSOR_TRACE_ID, CODEX_SANDBOX, etc.)
5. Filesystem markers (/opt/.devin)

Returns nil when no agent is detected (a.k.a. a human is typing).

API

Skill management

Runtime detection

RuntimeAgent has three fields: Name (e.g. "claude-code"), DisplayName (e.g. "Claude Code"), and EnvVar (the variable that matched, e.g. "CLAUDECODE").

Upstream sync

Agent directories are sourced from vercel-labs/skills. Runtime env vars are cross-referenced with vercel/vercel detect-agent. A weekly agentic workflow keeps both in sync.

40 agents supported. Run instill.AgentNames() for the full list, or see agents.go.