agent-developer

agent-developer is an agent for Claude Code from arpitnath/claude-capsule-kit. It costs 36 tokens per session (1,456 once invoked), scanned A, original, MIT.

A read-only guide for designing and troubleshooting AI agents and MCP integrations. MCP is a standard way for an agent to discover and use external tools.

In plain words
What is it for?
Use it when building mini-agents, choosing between single-purpose or coordinating agents, connecting MCP servers, or investigating agent behaviour.
Why use it?
It gives developers a structured way to reason about agent architecture, tool access, debugging, and testing instead of guessing at problems.

Agent for Claude Code

Written for Claude Code: a Claude Code subagent (agents/*.md). Also seen: model in frontmatter; mentions subagents.

Good fit Use it when building mini-agents, choosing between single-purpose or coordinating agents, connecting MCP servers, or investigating agent behaviour.

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Install with agentmods
npx agentmods add agents/arpitnath/claude-capsule-kit/agent-developer
Install

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.

Clone the repo
git clone --depth 1 https://github.com/arpitnath/claude-capsule-kit

Made for: Claude Code.

Wrote 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.

agentmods badge for agent-developer

README.md
[![agentmods](https://agentmods.dev/badge/agents/arpitnath/claude-capsule-kit/agent-developer/github.svg)](https://agentmods.dev/agents/arpitnath/claude-capsule-kit/agent-developer)
Your own site
<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.

agentmods 80×15 button for agent-developer

Your own site · 80×15
<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>
Per session 36 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,456 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce 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

Measured 1mo ago against content hash 9d10d3b9f990, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

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.

agents/agent-developer.md · 207 lines

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:

  1. Agent Patterns: Architecture and design patterns
  2. MCP Integration: Model Context Protocol best practices
  3. Tool Usage: How agents use tools effectively
  4. Debugging: Common issues and solutions
  5. 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

  1. Instructions/System Prompt: Agent's role and capabilities
  2. Tools: Functions the agent can call
  3. Model: LLM powering the agent (GPT-4, Claude, etc.)
  4. Context: State and memory management
  5. Handlers: Response processing logic

Development Strategy

Phase 1: Agent Design

  1. Define Purpose: What problem does this agent solve?
  2. Identify Tools: What capabilities are needed?
  3. Choose Model: Which LLM is appropriate?
  4. Design Flow: Input → Processing → Output

Phase 2: Implementation

  1. Create Agent Class: Extend base Agent class
  2. Configure Instructions: Clear, specific system prompt
  3. Add Tool Integration: MCP servers or direct tools
  4. Implement Execute Logic: Core agent behavior

Read the full file on GitHub · 207 lines

Changes

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.

  1. 1mo ago First seen · 207 lines · 36 tokens per session scan A 9d10d3b9f990

Subscribe to this mod's changes

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.

Related

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