building-agents SKILL.md skillA
building-agents from ampcode/official-plugins is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add ampcode/official-plugins/building-agents@git:20260929.7201b9dPins git:20260929.7201b9d in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- ampcode/official-plugins
- Path
skills/building-agents/SKILL.md- Versions recorded
- 2
- Latest version
- git:20260929.7201b9d, committed Sep 29, 2026
- First version recorded
- Sep 28, 2026
- Size
- 10,363 bytes
- Repository stars
- 21
- License
- none declared
Creates, edits, lists, and deletes custom agents (personal or workspace) with the manage_custom_agents tool: writes their instructions, picks their MCP servers, tools, and runtime, and saves drafts as it goes. Use when asked to build, set up, change, or remove a custom agent, or when the request comes from the agent builder page. Load FIRST, before calling manage_custom_agents.
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# Building Custom Agents ## What a custom agent is A custom agent is a saved agent mode a person or workspace owns. It is a directory `agents/<key>/` in their plugins repository with two files: `agent.ts` (the config: label, description, color, runtime, MCP servers, tools) and `instructions.md` (its system prompt, layered on top of Amp's base prompt). Once saved and not a draft, it shows up in the agent picker of every new thread, and threads that run it get its instructions plus a generated list of its MCP servers and how to call them. The `manage_custom_agents` tool reads and writes those files. It has four actions: - `list`: every agent the person can see, whether they may write workspace agents, the workspace name, and the MCP servers configured for them (`id`, `name`, `scope`, `connected`). - `get`: one agent's full config and instructions. - `put`: create or fully replace one agent. Send the complete agent every time, not a diff. - `delete`: remove one agent. Only after the person explicitly asks. ## Workflow 1. Call `list` first. It tells you which keys are taken, which MCP servers exist and whether the …
Read the whole file at its exact version.
How to install
mdr add ampcode/official-plugins/building-agents@sha256:af8bc81cf7474c22The line at the top of this page pins the label git:20260929.7201b9d, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_puc4cqcherxsgycb)
2 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 2 versions of this file, between Sep 28, 2026 and Sep 29, 2026, more than one a day.
| version | committed | commit | size | audit | |
|---|---|---|---|---|---|
| git:20260929.7201b9d latest | 2026-09-29 | 7201b9d | 10,363 B | A | view · diff |
| git:20260928.7085300 | 2026-09-28 | 7085300 | 10,328 B | A | view |
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (10363 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
ampcode/official-plugins · 21 stars · license none declared · pushed 2026-11-01 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_puc4cqcherxsgycb GET https://markdownregistry.com/api/v1/resolve?ref=ampcode/official-plugins/building-agents GET https://markdownregistry.com/api/v1/blob/af8bc81cf7474c22a0120a63887aef43da390882a47258e1261ed37d67213d06
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.
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