agent-stdlib

A standard library for building agents.

Anthropic's engineering blog documents how to build, evaluate, and run agents in production. Most of that knowledge never ships as something you can install; it stays prose you reopen when you hit the problem it solves. agent-stdlib packages the parts nobody else has: Claude Code skills, a few MCP servers, and a tool-gating hook.

Each component names the article it comes from and says how it differs from any skill that already covers similar ground. The pack ships only what was missing. Topics that strong community skills already handle stay out, with pointers below.

Skills

Skill	What it gives you	Source article
build-agent-evals	Build automated evals for an agent: pick a grader, choose pass@k vs pass^k, run the zero-to-one roadmap	Demystifying evals for AI agents
calibrate-eval-infrastructure	Stop container resource limits from swinging benchmark scores more than the models do	Quantifying infrastructure noise in agentic coding evals
coding-agent-scaffold	Design the two-tool (bash + file editor) interface for a coding agent so the model stops misusing it	Raising the bar on SWE-bench Verified
durable-agent-architecture	Split an agent service into brain, hands, and session so any part can crash and resume	Scaling Managed Agents
sandboxing-agentic-systems	Contain an agent that runs code or reads untrusted content, layer by layer	How we contain Claude
defending-against-prompt-injection	Keep an agent from obeying instructions hidden in the pages, emails, and files it reads	Mitigate jailbreaks and prompt injection
using-the-think-step	Decide when a mid-task reasoning step helps and how to prompt for it	The "think" tool
multi-agent-orchestration	Run an orchestrator-worker research system with parallel subagents	How we built our multi-agent research system
parallel-autonomous-agents	Coordinate unsupervised agents on one git repo with lock files and an autonomy loop	Building a C compiler with parallel Claudes

Install

Add the marketplace and install the plugin:

/plugin marketplace add pebeto/agent-stdlib
/plugin install agent-stdlib@agent-stdlib

Skills trigger themselves when a task matches their description. You can also load one explicitly with the Skill tool.

MCP servers

Three servers live under mcp-servers/, each paired with a skill. They need uv, which installs each server's one dependency from the script header on first run.

• think (enabled). The no-op think tool, paired with using-the-think-step.
• tool-gateway (enabled). search_tools and call_tool over a larger catalog, so the agent reaches many tools through two. Paired with the tool-scaling guidance in advanced-tool-use.
• code-execution (opt-in). Presents tools as importable code and runs composed Python in a subprocess. It executes model-written code, so it is not enabled by default. Turn it on once you have wrapped it in real isolation; see mcp-servers/code-execution/README.md and the sandboxing-agentic-systems skill.

think and tool-gateway are wired into the plugin's .mcp.json. To enable code-execution, point your client's MCP config at uv run .../mcp-servers/code-execution/server.py.

Commands, agent, and hooks

• /research <question> runs the orchestrator-worker flow: it decomposes the question, dispatches research-worker subagents in parallel, and synthesizes a cited answer. Paired with multi-agent-orchestration.
• /autonomous-loop sets up lock-file coordination for unsupervised agents on one repo, using scripts/locks.py and scripts/autonomy_loop.sh. Paired with parallel-autonomous-agents.
• action-gating is a PreToolUse hook that tiers Bash commands by risk and denies or asks on the dangerous ones. It stays off until you set AGENT_STDLIB_GATING=warn or enforce, and it only ever adds friction. See hooks/README.md.
• injection-screening is a PostToolUse hook that flags likely prompt-injection markers in fetched tool output and, on a hit, warns the agent or blocks it from acting until you confirm. Off until you set AGENT_STDLIB_INJECTION=warn or enforce. Paired with defending-against-prompt-injection. See hooks/README.md.

Beyond Claude Code

Most of this pack is not Claude-specific. The MCP servers speak the open MCP protocol, the scripts are plain Python and Bash, and the skill content is harness-neutral procedural knowledge. To use it in OpenCode, Cursor, Cline, or a custom agent on any model, see AGENTS.md, which maps each component to its portable form.

Already covered elsewhere

These topics from the same blog have solid community skills, so they stay out of this pack. Reach for these instead:

• Choosing an agent pattern (prompt chaining, routing, orchestrator-workers): markpitt/claude-skills → agent-patterns
• Context engineering (compaction, note-taking, just-in-time retrieval): muratcankoylan/agent-skills-for-context-engineering
• Designing agent or MCP tools (consolidation, namespacing, token-efficient responses): the same pack's tool-design
• Long-running build harness (initializer + coding agent, git-tracked state): eddiearc/long-running-harness
• GAN-style generator/evaluator harness: affaan-m/everything-claude-code → gan-style-harness
• Contextual retrieval RAG: packaged versions exist on mcpmarket

Provenance

This pack distills public writing on the Anthropic engineering blog. It is an independent project with no endorsement from Anthropic, and it ships no Anthropic code.

Contributing

See CONTRIBUTING.md. Each skill stands alone in skills/<name>/SKILL.md and opens with the article it distills.

License

MIT. See LICENSE.