mcp-authoring

mcp-authoring is a skill for Claude Code, Codex from omnigentx/jarvis. It costs 80 tokens per session (3,735 once invoked), scanned A, original, MIT.

A guide for adding and managing MCP servers. MCP, or Model Context Protocol, lets an agent connect to external tools and services.

In plain words
What is it for?
Use it to discover servers, install or attach existing ones, create custom tool connections, fix failing tools, or detach a server from an agent.
Why use it?
It helps determine what servers are available, avoid duplicate setup, and diagnose or remove broken connections safely.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to discover servers, install or attach existing ones, create custom tool connections, fix failing tools, or detach a server from an agent.

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Install with agentmods
npx agentmods add skills/omnigentx/jarvis/mcp-authoring
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.

Any agent
npx skills add omnigentx/jarvis --skill mcp-authoring
Clone the repo
git clone --depth 1 https://github.com/omnigentx/jarvis

Made for: Claude Code, Codex.

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 mcp-authoring

README.md
[![agentmods](https://agentmods.dev/badge/skills/omnigentx/jarvis/mcp-authoring.svg)](https://agentmods.dev/skills/omnigentx/jarvis/mcp-authoring)
Your own site
<a href="https://agentmods.dev/skills/omnigentx/jarvis/mcp-authoring"><img src="https://agentmods.dev/badge/skills/omnigentx/jarvis/mcp-authoring.svg" alt="Measured on agentmods" height="20"></a>
Per session 80 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,735 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 2 findings, up to high

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • high Tool Misuse · line 157
    Tool parameters are crafted to achieve unintended or unsafe behavior. Parameter abuse can bypass intended safety checks (e.g. shell=True, --force, dangerous glob patterns).
    Fix: Validate all tool parameters against an allowlist. Reject dangerous parameter values (shell=True, --force, -rf /) and use safe defaults.
  • medium Excessive Agency · line 195
    Skill grants unrestricted tool access without appropriate constraints. An agent with unfettered tool access can perform arbitrary actions including file modification, network requests, and code execution.
    Fix: Restrict tool access to only the tools required for the skill's stated purpose. Use an explicit allowlist rather than granting blanket access.
How audits are shown
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 $0.00080 $0.03735
Opus 5 $0.00040 $0.01868
Sonnet 5 $0.00016 $0.00747
Haiku 4.5 $0.00008 $0.00374

Measured 8d ago against content hash 6a339c87afbb, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

mcp-authoring 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 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.

Runs shell commandslowCapability

Expected in a hook, worth knowing in a rule or an instructions file.

- `eval()`, `exec()`, `os.system()` — use `subprocess.run([...])` instead
backend/.fast-agent/skills/mcp-authoring/SKILL.md · 374 lines

How it starts

The opening of the file, as written. The whole thing — 374 lines — stays where its author put it; the contents beside it link to each section on GitHub.

MCP AUTHORING & USAGE

You can extend yourself with new MCP servers via the mcp_admin tools, AND you can inspect/attach/detach existing ones. Read the matching section below for the situation in front of you.

Decision tree — pick the section

Situation Section
"What MCPs do I have? / Show me the catalog" Discovery
"Install jq / add the github MCP / register this URL" — server already exists Path A
"I need a custom tool that doesn't exist anywhere" Path B
"Tool X is broken / silently failing" Hot-fix then re-verify
"Detach this server from agent Y" mcp_detach_from_agent (one call)

Discovery — inspect before mutating

Before adding/changing anything, find out what's already there. The right tool depends on what you actually need to know:

You need… Call Cost
List of catalog server names + transport + who's attached mcp_list_servers() compact (~80 chars/server)
Full config of ONE server (command, args, env, cwd) mcp_get_server(name="…") small
Full config of EVERY server (rare — usually wrong) mcp_list_servers(verbose=True) heavy (~500 chars/server × N)
Live tool list + descriptions for one server mcp_test_server(name="…") spawn subprocess, descriptions auto-trimmed to 240 chars
Generated (Path-B) workspace inventory mcp_list_generated() compact (just tool names)
Full manifest + history of one generated server mcp_get_generated(name="…") larger

Default to compact lists. The catalog has ~28 servers; calling the verbose version pulls ~13 KB into context. Get the names compactly, then mcp_get_server(name) only the ones you'll actually act on.

Path A vs Path B — never mix

Situation Flow
Server already exists as an npm/pypi package or a hosted URL Path A (config-only)
You'd need to write the tool code yourself Path B (scaffold-then-test)

If you start Path B and then realize an existing package solves the problem, drop the scaffold (mcp_clean_workspace(scope="<name>")) and restart in Path A.

Read the full file on GitHub · 374 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. 8d ago First seen · 374 lines · 80 tokens per session scan A 6a339c87afbb

Subscribe to this mod's changes

mcp-authoring is a skill published in the GitHub repository omnigentx/jarvis (37 stars, last pushed 12d ago), licensed MIT. It adds 80 tokens to every session and 3,735 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 1 finding (runs shell commands). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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