Skill types
Every skill is one of three types: Custom prompt, Package (Anthropic-compatible), or Tool-based. You choose the type in the creation wizard, and you cannot change it later without recreating the skill — so it is worth understanding the differences first.
Custom prompt
A Custom prompt skill is a block of instructions the model follows when the skill is loaded. You write the instructions directly in the Prompt & tools tab of the editor, and Harriet delivers them to the AI whenever the skill is active for that person. If the instructions field is left empty, the skill's description is used instead.
Prompt skills can carry tools too: connect one or more MCP connectors and their tools travel with the skill. That makes this type a good fit for pairing know-how with a system: for example, instructions on how to triage bugs, connected to your issue tracker.
Package (Anthropic-compatible)
A Package skill is a folder of files built around a SKILL.md at the root (YAML front matter with name and description, followed by Markdown instructions) plus optional files such as references/… and small scripts. The wizard describes it as "Import or author a multi-file skill package (SKILL.md, forms, scripts). Supports GitHub sync and zip import."
Packages are the format Harriet shares with the wider Anthropic skills ecosystem: a package you author for Harriet works in other Anthropic-compatible runtimes, and packages published elsewhere can be imported. Files are managed in the Anthropic package tab, uploaded as a zip, or kept in sync from a GitHub repository. The details live on Skill packages.
One rule to know: package files and fallback instructions are mutually exclusive. Either the skill has an explicit SKILL.md file, or it uses its prompt text as the skill content; the editor prevents mixing the two.
Tool-based
A Tool-based skill is built on a Harriet tool template: a pre-registered set of tools maintained by Harriet, chosen from the Tool template dropdown when you create the skill. The wizard describes it as "Use a built-in Harriet tool template as the skill foundation, with optional extra instructions." You add your own guidance on top, but the tools themselves come from the template.
Choose this type when the capability is defined by actions rather than knowledge, and a template already exists for the system you care about. For tools from your own integrations, use a Custom prompt or Package skill with a connector attached instead.
Comparing the three
| Custom prompt | Package (Anthropic-compatible) | Tool-based | |
|---|---|---|---|
| When to use | Playbooks, tone, and process knowledge; quick to author and iterate | Multi-file skills, anything shared with the Anthropic ecosystem, skills maintained in a repo | Capabilities defined by a built-in Harriet tool template |
| What it contains | Prompt text, plus optional MCP connectors | SKILL.md, optional references/… and scripts, plus optional MCP connectors | A tool template, plus optional extra instructions |
| How it updates | Edit the prompt and save | Edit files in the editor, re-import a zip, or scheduled GitHub sync | Harriet maintains the template; you edit only your added instructions |
Not sure which to pick? Start with a Custom prompt. If the skill grows past one page of instructions or needs supporting files, recreate it as a Package; the wizard makes that a five-minute job.