model-context-builder

model-context-builder is a skill for Claude Code from bobmatnyc/claude-mpm-skills. It costs 28 tokens per session (5,338 once invoked), scanned A, original, MIT.

A guide to evaluating MCP servers. MCP, or Model Context Protocol, is a way for AI agents to use tools and data provided by external servers.

In plain words
What is it for?
Use it to create read-only evaluation questions, test multi-step tool use, and verify that answers are stable and independently checkable.
Why use it?
It helps reveal whether an MCP server's tools and descriptions let an agent answer realistic questions accurately, rather than merely checking whether the server runs.

Skill for Claude Code

Written for Claude Code: disable-model-invocation in frontmatter. Also seen: mentions subagents.

Needs its repository: it runs a file that does not travel with it, so clone the repository first. The line is python scripts/evaluation.py \.

Good fit Use it to create read-only evaluation questions, test multi-step tool use, and verify that answers are stable and independently checkable.

Compare 6 skills from other repositories ↓
Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo
git clone --depth 1 https://github.com/bobmatnyc/claude-mpm-skills
agentmods
npx agentmods add skills/bobmatnyc/claude-mpm-skills/model-context-builder

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 model-context-builder

README.md
[![agentmods](https://agentmods.dev/badge/skills/bobmatnyc/claude-mpm-skills/model-context-builder/github.svg)](https://agentmods.dev/skills/bobmatnyc/claude-mpm-skills/model-context-builder)
Your own site
<a href="https://agentmods.dev/skills/bobmatnyc/claude-mpm-skills/model-context-builder"><img src="https://agentmods.dev/badge/skills/bobmatnyc/claude-mpm-skills/model-context-builder/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 model-context-builder

Your own site · 80×15
<a href="https://agentmods.dev/skills/bobmatnyc/claude-mpm-skills/model-context-builder"><img src="https://agentmods.dev/badge/skills/bobmatnyc/claude-mpm-skills/model-context-builder.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 28 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 5,338 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. 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 Excessive Agency · line 499
    Skill selects an external model or provider that may use a different account or billing plan than the operator expects. Undisclosed model switches can cause unexpected cost or quota consumption.
    Fix: Remove the model/provider override or disclose it prominently and require explicit operator approval before invoking an external coding CLI or billed model.
  • medium Excessive Agency · line 216
    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 $0.00028 $0.05338
Opus 5 $0.00014 $0.02669
Sonnet 5 $0.00006 $0.01068
Haiku 4.5 $0.00003 $0.00534

Measured 9d ago against content hash 80613319b98b, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

model-context-builder 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 9d 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.

universal/main/model-context-builder/SKILL.md · 646 lines

How it starts

The opening of the file, as written. The whole thing — 646 lines — stays where its author put it; the contents beside it link to each section on GitHub.

MCP Server Evaluation Guide

Overview

This document provides guidance on creating comprehensive evaluations for MCP servers. Evaluations test whether LLMs can effectively use your MCP server to answer realistic, complex questions using only the tools provided.


Quick Reference

Evaluation Requirements

  • Create 10 human-readable questions
  • Questions must be READ-ONLY, INDEPENDENT, NON-DESTRUCTIVE
  • Each question requires multiple tool calls (potentially dozens)
  • Answers must be single, verifiable values
  • Answers must be STABLE (won't change over time)

Output Format

<evaluation>
   <qa_pair>
      <question>Your question here</question>
      <answer>Single verifiable answer</answer>
   </qa_pair>
</evaluation>

Purpose of Evaluations

The measure of quality of an MCP server is NOT how well or comprehensively the server implements tools, but how well these implementations (input/output schemas, docstrings/descriptions, functionality) enable LLMs with no other context and access ONLY to the MCP servers to answer realistic and difficult questions.

Evaluation Overview

Create 10 human-readable questions requiring ONLY READ-ONLY, INDEPENDENT, NON-DESTRUCTIVE, and IDEMPOTENT operations to answer. Each question should be:

  • Realistic
  • Clear and concise
  • Unambiguous
  • Complex, requiring potentially dozens of tool calls or steps
  • Answerable with a single, verifiable value that you identify in advance

Question Guidelines

Core Requirements

  1. Questions MUST be independent

    • Each question should NOT depend on the answer to any other question
    • Should not assume prior write operations from processing another question
  2. Questions MUST require ONLY NON-DESTRUCTIVE AND IDEMPOTENT tool use

    • Should not instruct or require modifying state to arrive at the correct answer
  3. Questions must be REALISTIC, CLEAR, CONCISE, and COMPLEX

    • Must require another LLM to use multiple (potentially dozens of) tools or steps to answer

Read the full file on GitHub · 646 lines

Files

What ships with it

1 file 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.

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. 9d ago First seen · 646 lines · 28 tokens per session scan A 80613319b98b

Subscribe to this mod's changes

model-context-builder is a skill published in the GitHub repository bobmatnyc/claude-mpm-skills (75 stars, last pushed 1mo ago), licensed MIT. It adds 28 tokens to every session and 5,338 once invoked, about $0.0001 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 2026-09-03.

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