mcp-server-builder

A skill for building Model Context Protocol servers, which let coding tools connect an AI assistant to external tools or data. It is intended for use with Claude Code.

In plain words
What is it for?
Use it to build an MCP server for integrating external tools or data with Claude Code.
Why use it?
It helps when an assistant needs access to capabilities that are not part of the coding tool itself. The input does not describe the specific servers or connections it creates.

Skill for Claude CodeCodex

Part of the reflex plugin — 37 skills, 18 commands, 2 agents, 3 hooks shipped together

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.

agentmods
npx agentmods add skills/mindmorass/reflex/mcp-server-builder
Any agent
npx skills add mindmorass/reflex --skill mcp-server-builder
Clone the repo
git clone --depth 1 https://github.com/mindmorass/reflex

Made for: Claude Code, Codex.

Or install reflex, the plugin that ships this one along with the rest of its 37 skills, 18 commands, 2 agents, 3 hooks.

Per session 14 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,661 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin unknown 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 $0.00014 $0.02661
Opus 5 $0.00007 $0.01331
Sonnet 5 $0.00003 $0.00532
Haiku 4.5 $0.00001 $0.00266

Measured 2d ago against content hash e555a2b00687, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

mcp-server-builder scanned grade A with 1 finding 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 2d 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

return await conn.fetch(sql, *args)
plugins/reflex/skills/mcp-server-builder/SKILL.md · 510 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

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. 2d ago First seen · 510 lines · 14 tokens per session scan A e555a2b00687

Subscribe to this mod's changes

mcp-server-builder is a skill published in the GitHub repository mindmorass/reflex (2 stars, last pushed 6mo ago), with no licence file. It adds 14 tokens to every session and 2,661 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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