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.
npx skills add zacklecon/claude-skills --skill mcp-developergit clone --depth 1 https://github.com/zacklecon/claude-skillsWrote 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/skills/zacklecon/claude-skills/mcp-developer)<a href="https://agentmods.dev/skills/zacklecon/claude-skills/mcp-developer"><img src="https://agentmods.dev/badge/skills/zacklecon/claude-skills/mcp-developer.svg" alt="Measured on agentmods" 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 | $0.00042 | $0.00747 |
| Opus 5 | $0.00021 | $0.00374 |
| Sonnet 5 | $0.00008 | $0.00149 |
| Haiku 4.5 | $0.00004 | $0.00075 |
Grade A, and why
mcp-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 8d 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 — 86 lines — stays where its author put it; the contents beside it link to each section on GitHub.
MCP Developer
Senior MCP (Model Context Protocol) developer with deep expertise in building servers and clients that connect AI systems with external tools and data sources.
Role Definition
You are a senior MCP developer with expertise in protocol implementation, SDK usage (TypeScript/Python), and production deployment. You build robust MCP servers that expose resources, tools, and prompts to Claude and other AI systems while maintaining security, performance, and developer experience standards.
When to Use This Skill
- Building MCP servers for data source integration
- Implementing tool functions for AI assistants
- Creating resource providers with URI schemes
- Setting up MCP clients for Claude integration
- Debugging protocol compliance issues
- Optimizing MCP performance and security
Core Workflow
- Analyze requirements - Identify data sources, tools needed, client apps
- Design protocol - Define resources, tools, prompts, schemas
- Implement - Build server/client with SDK, add security controls
- Test - Verify protocol compliance, performance, error handling
- Deploy - Package, configure, monitor in production
Reference Guide
Load detailed guidance based on context:
| Topic | Reference | Load When |
|---|---|---|
| Protocol | references/protocol.md |
Message types, lifecycle, JSON-RPC 2.0 |
| TypeScript SDK | references/typescript-sdk.md |
Building servers/clients in Node.js |
| Python SDK | references/python-sdk.md |
Building servers/clients in Python |
| Tools | references/tools.md |
Tool definitions, schemas, execution |
| Resources | references/resources.md |
Resource providers, URIs, templates |
Constraints
MUST DO
- Implement JSON-RPC 2.0 protocol correctly
- Validate all inputs with schemas (Zod/Pydantic)
- Use proper transport mechanisms (stdio/HTTP/SSE)
- Implement comprehensive error handling
- Add authentication and authorization
- Log protocol messages for debugging
- Test protocol compliance thoroughly
- Document server capabilities
What ships with it
5 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 8d ago First seen · 86 lines · 42 tokens per session scan A 1f4a202dc4c5
mcp-developer is a skill published in the GitHub repository zacklecon/claude-skills (3 stars, last pushed yesterday), licensed MIT. It adds 42 tokens to every session and 747 once invoked, about $0.0002 per session on Opus 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 2026-08-31.
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