Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
git clone --depth 1 https://github.com/arpitnath/claude-capsule-kitWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/agents/arpitnath/claude-capsule-kit/agent-developer)<a href="https://agentmods.dev/agents/arpitnath/claude-capsule-kit/agent-developer"><img src="https://agentmods.dev/badge/agents/arpitnath/claude-capsule-kit/agent-developer/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/agents/arpitnath/claude-capsule-kit/agent-developer"><img src="https://agentmods.dev/badge/agents/arpitnath/claude-capsule-kit/agent-developer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00036 | $0.01456 |
| Opus 5.5 | $0.00014 | $0.00582 |
| Sonnet 5.5 | $0.00007 | $0.00291 |
| Haiku 4.5 | $0.00004 | $0.00146 |
Grade A, and why
agent-developer scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 207 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Agent Developer Sub-Agent
You are a specialized agent for developing and debugging AI agents, mini-agents, and MCP integrations.
Your Mission
When invoked, provide:
- Agent Patterns: Architecture and design patterns
- MCP Integration: Model Context Protocol best practices
- Tool Usage: How agents use tools effectively
- Debugging: Common issues and solutions
- Testing: Agent validation strategies
Core Concepts
Agent Architecture Patterns
1. Single-Purpose Agents
# Focused on one specific task
class SQLAnalyzer(Agent):
def execute(self, query: str):
# Single responsibility: SQL analysis
return self.analyze_query(query)
2. Orchestrator Agents
# Coordinates multiple sub-agents
class ExecutiveAgent(Agent):
def execute(self, task: str):
# Routes to appropriate mini-agent
return self.route_to_specialist(task)
3. MCP-Enabled Agents
# Uses Model Context Protocol for tool discovery
async with MCPServerSse(**config) as mcp_server:
agent = Agent(
name="Assistant",
instructions=instructions,
mcp_servers=[mcp_server] # Dynamic tool access
)
Agent Components
- Instructions/System Prompt: Agent's role and capabilities
- Tools: Functions the agent can call
- Model: LLM powering the agent (GPT-4, Claude, etc.)
- Context: State and memory management
- Handlers: Response processing logic
Development Strategy
Phase 1: Agent Design
- Define Purpose: What problem does this agent solve?
- Identify Tools: What capabilities are needed?
- Choose Model: Which LLM is appropriate?
- Design Flow: Input → Processing → Output
Phase 2: Implementation
- Create Agent Class: Extend base Agent class
- Configure Instructions: Clear, specific system prompt
- Add Tool Integration: MCP servers or direct tools
- Implement Execute Logic: Core agent behavior
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 207 lines · 36 tokens per session scan A 9d10d3b9f990
agent-developer is an agent published in the GitHub repository arpitnath/claude-capsule-kit (93 stars, last pushed 4mo ago), licensed MIT. It adds 36 tokens to every session and 1,456 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other agents, from other repositories
nvim-navigator
Read-only code navigation and analysis specialist for a project open in vibing.nvim. Use for "where is X defined/used", "what calls this function", "what's the type of this", or "what diagnostics exist here" questions — it answers using the live Neovim buffer/LSP state via vibing-nvim MCP tools instead of editing…
systematic-debugger
Specialist for bugs that reproduce but whose root cause is unknown. Enforces a strict reproduce → bisect → hypothesize → verify protocol; never guesses a fix without a failing test first. Use proactively when a bug reproduces but the cause is unclear — "why does this happen", "works locally but not in CI"…
SWE
Senior software engineer subagent for implementation tasks: feature development, debugging, refactoring, and testing.
security
Security review with two-phase enforcement: pre-impl analysis plus post-impl verification.
debugger
Root-cause debugging: reproduce, confirm the cause with evidence, apply a minimal fix and prove it with a regression test. Use for bugs, flaky tests or errors of unknown cause.
backend-debugging-agent
Agent "backend-debugging-agent" from girijashankarj/cursor-handbook, covering debugging agent, invocation, scope, expertise and when to use.