Step-file frontmatter

An llm or confirmation step can read its prompt from a Markdown file. That file may begin with an optional YAML frontmatter block, fenced by ---, followed by the Liquid prompt body:

---
id: greet
description: Generate a personalized greeting
---
Generate a warm, friendly greeting for {{ inputs.name }}.
Keep it to one sentence.

Everything below the closing --- is the prompt template. The frontmatter is optional — a step file with no fence is treated as a pure prompt.

Default file path

A step points at its file with the file key in skill.yaml. When a step omits file and has no inline message, Skiller looks for the file at steps/NN-<id>.md, where NN is the step’s two-digit position and <id> is the step id. The first step greet resolves to steps/01-greet.md, the second fact step to steps/02-fact.md, and so on.

Set file explicitly to override this convention.

Keys

Key	Type	Notes
id	string	Step identifier (see note below)
description	string	Human-readable description of the step
tool	string	A tool alias the step invokes
tools	list	MCP tool aliases the model may call
tool_mode	enum	auto (model decides) or required (must call a tool)
requires	list	Step ids that must run first

tool, tools, tool_mode, and requires are the same step-level options accepted on a manifest step. Declaring them in the step file keeps a step’s tool configuration next to the prompt it governs, rather than splitting it across the manifest. See the skill.yaml reference for what each option does.

Unlike the strict skill.yaml manifest, step-file frontmatter is parsed leniently — an unrecognized key is ignored rather than rejected.

Note

The frontmatter id does not have to match the step id in skill.yaml. The step id (and the order of the steps list) is what drives execution and the steps/NN-<id>.md path resolution; the frontmatter id is documentation for the prompt file itself.

Related

• skill.yaml reference — the manifest that points at each step file.
• Step types — how llm, confirmation, and tool steps run.