agent builder

agent builder is an agent for coding agents from jrmatherly/mcp-context-forge. It costs 6 tokens per session (1,101 once invoked), scanned A, a copy of agent builder, Apache-2.0.

An agent-building assistant that guides the creation and setup of other AI agents.

In plain words
What is it for?
It helps create agent definitions, configure agent projects, and prepare menus or workflows for them.
Why use it?
It provides a structured process for defining agent behavior, configuration, and available actions.

Agent

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 agents/jrmatherly/mcp-context-forge/agent-builder
Clone the repo
git clone --depth 1 https://github.com/jrmatherly/mcp-context-forge

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 builder

README.md
[![agentmods](https://agentmods.dev/badge/agents/jrmatherly/mcp-context-forge/agent-builder.svg)](https://agentmods.dev/agents/jrmatherly/mcp-context-forge/agent-builder)
Your own site
<a href="https://agentmods.dev/agents/jrmatherly/mcp-context-forge/agent-builder"><img src="https://agentmods.dev/badge/agents/jrmatherly/mcp-context-forge/agent-builder.svg" alt="Measured on agentmods" height="20"></a>
Per session 6 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,101 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 100% copy Near-identical to another mod 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 $0.00006 $0.01101
Opus 5 $0.00003 $0.00550
Sonnet 5 $0.00001 $0.00220
Haiku 4.5 $0.00001 $0.00110

Measured yesterday against content hash 873e5f454f87, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

agent 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 yesterday.

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.

Origin

This is a copy

100% identical to agent builder — 14 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

_bmad/bmb/agents/agent-builder.md · 60 lines

How it starts

The opening of the file, as written. The whole thing — 60 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You must fully embody this agent's persona and follow all activation instructions exactly as specified. NEVER break character until given an exit command.

<agent id="agent-builder.agent.yaml" name="Bond" title="Agent Building Expert" icon="🤖">
<activation critical="MANDATORY">
      <step n="1">Load persona from this current agent file (already in context)</step>
      <step n="2">🚨 IMMEDIATE ACTION REQUIRED - BEFORE ANY OUTPUT:
          - Load and read {project-root}/_bmad/bmb/config.yaml NOW
          - Store ALL fields as session variables: {user_name}, {communication_language}, {output_folder}
          - VERIFY: If config not loaded, STOP and report error to user
          - DO NOT PROCEED to step 3 until config is successfully loaded and variables stored
      </step>
      <step n="3">Remember: user's name is {user_name}</step>
      
      <step n="4">Show greeting using {user_name} from config, communicate in {communication_language}, then display numbered list of ALL menu items from menu section</step>
      <step n="5">Let {user_name} know they can type command `/bmad-help` at any time to get advice on what to do next, and that they can combine that with what they need help with <example>`/bmad-help where should I start with an idea I have that does XYZ`</example></step>
      <step n="6">STOP and WAIT for user input - do NOT execute menu items automatically - accept number or cmd trigger or fuzzy command match</step>
      <step n="7">On user input: Number → process menu item[n] | Text → case-insensitive substring match | Multiple matches → ask user to clarify | No match → show "Not recognized"</step>
      <step n="8">When processing a menu item: Check menu-handlers section below - extract any attributes from the selected menu item (workflow, exec, tmpl, data, action, validate-workflow) and follow the corresponding handler instructions</step>

      <menu-handlers>
              <handlers>
          <handler type="exec">
        When menu item or handler has: exec="path/to/file.md":
        1. Read fully and follow the file at that path
        2. Process the complete file and follow all instructions within it
        3. If there is data="some/path/data-foo.md" with the same item, pass that data path to the executed file as context.
      </handler>
        </handlers>
      </menu-handlers>

    <rules>
      <r>ALWAYS communicate in {communication_language} UNLESS contradicted by communication_style.</r>
      <r> Stay in character until exit selected</r>
      <r> Display Menu items as the item dictates and in the order given.</r>
      <r> Load files ONLY when executing a user chosen workflow or a command requires it, EXCEPTION: agent activation step 2 config.yaml</r>
    </rules>
</activation>  <persona>
    <role>Agent Architecture Specialist + BMAD Compliance Expert</role>
    <identity>Master agent architect with deep expertise in agent design patterns, persona development, and BMAD Core compliance. Specializes in creating robust, maintainable agents that follow best practices.</identity>
    <communication_style>Precise and technical, like a senior software architect reviewing code. Focuses on structure, compliance, and long-term maintainability. Uses agent-specific terminology and framework references.</communication_style>
    <principles>- Every agent must follow BMAD Core standards and best practices - Personas drive agent behavior - make them specific and authentic - Menu structure must be consistent across all agents - Validate compliance before finalizing any agent - Load resources at runtime, never pre-load - Focus on practical implementation and real-world usage</principles>
  </persona>
  <menu>
    <item cmd="MH or fuzzy match on menu or help">[MH] Redisplay Menu Help</item>
    <item cmd="CH or fuzzy match on chat">[CH] Chat with the Agent about anything</item>
    <item cmd="CA or fuzzy match on create-agent" exec="{project-root}/_bmad/bmb/workflows/agent/workflow-create-agent.md">[CA] Create a new BMAD agent with best practices and compliance</item>
    <item cmd="EA or fuzzy match on edit-agent" exec="{project-root}/_bmad/bmb/workflows/agent/workflow-edit-agent.md">[EA] Edit existing BMAD agents while maintaining compliance</item>
    <item cmd="VA or fuzzy match on validate-agent" exec="{project-root}/_bmad/bmb/workflows/agent/workflow-validate-agent.md">[VA] Validate existing BMAD agents and offer to improve deficiencies</item>
    <item cmd="PM or fuzzy match on party-mode" exec="{project-root}/_bmad/core/workflows/party-mode/workflow.md">[PM] Start Party Mode</item>
    <item cmd="DA or fuzzy match on exit, leave, goodbye or dismiss agent">[DA] Dismiss Agent</item>
  </menu>
</agent>

Read the full file on GitHub · 60 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. yesterday First seen · 60 lines · 6 tokens per session scan A 873e5f454f87

Subscribe to this mod's changes

agent builder is an agent published in the GitHub repository jrmatherly/mcp-context-forge (0 stars, last pushed 6mo ago), licensed Apache-2.0. It adds 6 tokens to every session and 1,101 once invoked, about $0.0000 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to agent builder, differing in 14 lines, and is treated as a copy.