AGENTS.md file for agents

AGENTS.md is a plain text file in the root of your project that AI agents read before they start working. Jantaris serves a ready version at https://jantaris.com/agents.md. Once it is in your repo, the agent knows how to authenticate, how to request an image or video with POST /v1/generate, how to poll a task, how to talk to chat models and how to connect the MCP server. You do not have to explain anything.

What the file contains

• base URL https://jantaris.com/v1 and the header Authorization: Bearer $JANTARIS_API_KEY,
• cost rules: reservation before start, failed generation costs 0, codes 402 and 403,
• the model catalog (GET /v1/models, GET /v1/models/{id}) and the rule "read the schema before sending input",
• curl examples: image, video with polling, song with lyrics, chat,
• signed webhooks,
• MCP setup for Claude Code, Codex CLI and Cursor,
• an error table and a warning that POST /v1/generate is not idempotent.

Add it to your repo

Open a terminal in the root folder of your project.

macOS and Linux

curl -fsSL https://jantaris.com/agents.md -o AGENTS.md

Already have your own AGENTS.md? Append instead of overwriting:

curl -fsSL https://jantaris.com/agents.md >> AGENTS.md

Windows PowerShell

Invoke-WebRequest -Uri "https://jantaris.com/agents.md" -OutFile "AGENTS.md"

Append to an existing file:

Invoke-RestMethod -Uri "https://jantaris.com/agents.md" | Add-Content -Path "AGENTS.md" -Encoding utf8

No terminal

Open https://jantaris.com/agents.md in your browser, select all (Ctrl+A or Cmd+A), copy and paste it into a new AGENTS.md file in your project folder.

Verify

head -5 AGENTS.md

Get-Content AGENTS.md -TotalCount 5

The first line is # AGENTS.md - Jantaris API. Then ask your agent: "According to AGENTS.md, how do I generate an image with Jantaris?". If it answers with POST /v1/generate and ?wait=60, the file works.

Which tools read it

For Claude Code, the quickest way:

echo "@AGENTS.md" >> CLAUDE.md

Add-Content -Path "CLAUDE.md" -Value "@AGENTS.md"

The key stays out of the repo

The file contains no key. The agent reads it from the JANTARIS_API_KEY environment variable, which you set once:

export JANTARIS_API_KEY="sk-jt-..."

[Environment]::SetEnvironmentVariable("JANTARIS_API_KEY", "sk-jt-...", "User")

Create the key in the dashboard, API keys tab. Give it a Monthly limit - an agent that can generate video should have a hard spending ceiling.

If you keep the key in a .env file, make sure .env is in .gitignore.

Your own rules below

Under the API description add rules for your project, for example:

## Project rules

- Before any video generation, state the cost (estimated_cost) and wait for my approval.
- Save images in public/img/ as .webp.
- Use nano-banana-pro for images and seedance-2.5 at 720p for video.
- Never generate more than 3 variants at once.

Updating

When we add endpoints or change examples, just download the file again with the command above. If you added your own rules, keep them in a separate section and paste them back after downloading, or move them to a separate file.

Common problems