Best Practices for Agentic Development

Use this as the master routing skill for agentic-development work. Load the reference file that matches the task before making design or implementation decisions.

Core principle: Agentic systems are engineered through behavior, context, tools, evals, and operational guardrails. Do not solve every problem with a larger prompt.

Route First

Pick the relevant reference:

Task	Read
Creating, editing, packaging, auditing, or testing skills	references/skill-development.md
Designing an agent product, tool-using assistant, memory layer, eval loop, or agent architecture	references/general-agent-development.md
Building multi-step software-development workflows with planning, subagents, verification, reviews, worktrees, and delivery gates	references/agentic-development.md
Designing or implementing MCP servers, MCP tools, tool schemas, resources, prompts, or context-efficient MCP workflows	references/mcp-development.md

If more than one applies, read the most specific file first, then read others only for missing concerns.

Universal Practices

Apply these across all agentic-development work:

1. State the behavior. Define what the agent should do in observable terms.
2. Choose the right enforcement surface. Use skills for judgment, tools/scripts for deterministic checks, hooks for runtime gates, and evals for behavioral confidence.
3. Use progressive disclosure. Keep always-loaded context small; load details on demand.
4. Prefer gates over rules. A gate blocks progress until objective evidence exists.
5. Test behavior under pressure. Normal prompts do not prove adherence.
6. Capture rationalizations. Convert observed excuses into red flags and counters.
7. Verify before claiming. Completion claims need fresh evidence.
8. Design for harness reality. Detect available tools, sandbox limits, worktree state, subagents, hooks, and native capabilities before acting.
9. Match guidance form to the failure shape. Prohibition, positive recipe, structural required field, or condition. Prohibition is not a universal fix. See skill-development.md.

Enforcement Surface Decision

Need	Use
Reusable judgment, workflow, or pattern	Skill
Large reference or examples	Markdown reference file
Repeated deterministic operation	Script or CLI
Runtime stop/continue/approval decision	Hook or wrapper
Agent-visible external capability	MCP tool
Large API or data processing without context bloat	MCP-exec-style fetch/filter/summarize workflow
Confidence that behavior holds	Eval harness with transcripts and assertions
Durable behavioral rule that must survive across turns	Re-inject into system prompt every turn (mutable rules file), not a one-time note or memory — see general-agent-development.md

Red Flags

Stop and re-evaluate when you think:

• "This is just prompt wording."
• "The agent will probably infer the right thing."
• "We can test later."
• "A bigger instruction block will fix it."
• "The tool schema can be verbose because context is large."
• "The subagent can just read the whole conversation."
• "The happy path worked once."
• "A prohibition list will fix this."

These are signs you need routing, gates, sharper context, or evals.

Completion Criteria

Before considering agentic-development work complete:

• Relevant reference file has been applied.
• Behavior is stated in observable terms.
• Triggering/discovery path is clear.
• Context-loading strategy is explicit.
• Failure modes and rationalizations are addressed.
• Deterministic checks are automated where possible.
• Verification or eval evidence exists for behavior-changing work.