Kit SDK

What it does

When your agent uses it

• The user asks to create a program
• Application that uses Kit programmatically as a Go library — e.g
• Kit extensions (use kit-extensions skill instead)

Example prompts

• “/kit-sdk”

Requirements

• A credential in ANTHROPIC_API_KEY

Workflow steps

3 steps, taken from the first numbered list in SKILL.md.

1. 1Create: kit.New(ctx, opts) — loads config, initializes MCP servers, creates LLM provider, sets up agent
2. 2Interact: host.Prompt(ctx, msg) — send messages, agent uses tools as needed
3. 3Close: host.Close() — cleans up MCP connections, model resources, session file handle

What it can do on your machine

Read from SKILL.md and the folder at commit 1eb0cb9. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Shell commands in SKILL.md call:

  • go

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  No URLs in SKILL.md.

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names these keys or tokens, usually read from environment variables:

  • ANTHROPIC_API_KEY

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Kit SDK loads about 2.6k tokens when it runs, and up to ~17k if it reads all its reference files. Until then it costs about 95 tokens; SKILL.md has 883 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~95

When it runs · the whole SKILL.md, loaded when a task matches

~2.6k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~17k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from mark3labs/kit at commit 1eb0cb9, republished under its MIT licence (© mark3labs). 883 words, ~2,634 tokens.

name

kit-sdk

description

Guide for building Go applications with the Kit SDK. Use when the user asks to create a program, service, script, or application that uses Kit programmatically as a Go library — e.g. embedding LLM interactions, building agents, creating CLI tools powered by Kit, or integrating Kit into backend services. Do NOT use for Kit extensions (use kit-extensions skill instead).

go get github.com/mark3labs/kit

import kit "github.com/mark3labs/kit/pkg/kit"

package main

import (
    "context"
    "fmt"
    "log"

    kit "github.com/mark3labs/kit/pkg/kit"
)

func main() {
    ctx := context.Background()

    host, err := kit.New(ctx, nil) // nil = load .kit.yml (cwd) then ~/.kit.yml defaults
    if err != nil {
        log.Fatal(err)
    }
    defer func() { _ = host.Close() }()

    response, err := host.Prompt(ctx, "What is 2+2?")
    if err != nil {
        log.Fatal(err)
    }
    fmt.Println(response)
}

defer func() { _ = host.Close() }()

type WeatherInput struct {
    City string `json:"city" description:"City name, e.g. 'San Francisco'"`
}

weatherTool := kit.NewTool("get_weather", "Get current weather for a city",
    func(ctx context.Context, input WeatherInput) (kit.ToolOutput, error) {
        return kit.TextResult("72°F, sunny in " + input.City), nil
    },
)

host, _ := kit.New(ctx, &kit.Options{
    ExtraTools: []kit.Tool{weatherTool},
})

© mark3labs, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 12 other files (references) in skills/kit-sdk of mark3labs/kit.

• SKILL.md
• references/common-patterns.md
• references/configuration.md
• references/context-compaction-subagents.md
• references/events.md
• references/extension-api-auth-skills.md
• references/hooks.md
• references/models-and-mcp.md
• references/options.md
• references/prompt-methods.md
• references/sessions.md
• references/tools.md
• references/types.md

Open the folder on GitHubat commit 1eb0cb9