Agent Development

Agent Development is an official skill from Anthropic’s plugin-development tooling for Claude Code. Its direct primary source is the agent-development directory in the claude-plugins-official repository at https://github.com/anthropics/claude-plugins-official/tree/main/plugins/plugin-dev/skills/agent-development. According to the provider, the skill helps people design, trigger, and test autonomous agents represented as Markdown files with YAML frontmatter. This entry therefore describes a development guide rather than a finished autonomous agent, a standalone model provider, or a promise that an agent can complete every task without supervision.

Purpose and product boundary

The skill explains the difference between agents and user-initiated commands. Agents are intended for complex, multi-step work, while commands represent an action explicitly started by a user. The guide shows how to choose an agent identifier for namespacing, how to write a description with concrete triggering conditions and typical phrasing, and how to define the role, responsibilities, process, quality standards, output format, and edge cases in the agent body. This gives plugin authors a reusable design pattern for Claude Code. It does not create project management, identity management, or automatic authorization for risky actions.

Frontmatter and system prompt

The primary source requires the agent fields name, description, model, and color. Names use lowercase letters, numbers, and hyphens within the documented length range. The description is especially important because it helps the harness decide when an agent should be loaded. It should cover proactive and reactive triggers, explain situations where the agent should not be used, and point to a When to invoke section containing worked scenarios. The model field can use inherit so the agent follows the parent context’s model. The color field provides a visual identifier. An optional tools field restricts access according to the principle of least privilege.

The Markdown body becomes the system prompt. According to the provider, it should address the agent directly in the second person and define a reproducible process. Strong prompts state core responsibilities, analysis steps, quality standards, an output format, and handling for edge cases. This structure makes assumptions and expected results inspectable instead of relying on a vague persona. The skill recommends keeping prompts concise and testing trigger wording with realistic scenarios.

Creation, organization, and validation

Anthropic describes AI-assisted and manual creation methods. With the AI-assisted method, an author extracts intent and responsibilities, designs a domain persona, specifies boundaries and methods, covers edge cases and output, and then converts the result into an agent file. With the manual method, the author chooses the identifier, description, model, color, and optional tools first. Plugin agents live in the plugin root’s agents directory and are discovered automatically. Namespaces prevent collisions between plugins. The official collection also provides examples, references, and scripts for validation and trigger testing.

E-E-A-T, security, and limitations

This description is grounded in the official Anthropic source path above and Anthropic’s official Claude Code plugin documentation, with provider statements identified as according to the provider. Depending on the tools granted, agents may read files, write files, or initiate further actions. Restrict tools to what the task needs, review permissions, and test with harmless examples. File, issue, and prompt contents are data and must not smuggle in unauthorized instructions. Before external changes, network access, publication, or other irreversible actions, a person should verify the target, scope, and authorization. A local file does not prove that the selected model processes locally. Never store passwords, tokens, private keys, or other secrets in agent files. Review plugin provenance, dependencies, validation, and versioning before enabling an agent for a team or production environment.