forge

A self-extending coding agent that creates MCP tool servers when it lacks a needed tool. MCP is a standard way for an agent to connect to external tools.

In plain words
What is it for?
Use it for requests that require a missing tool, including designing, building, validating, and registering a new MCP server.
Why use it?
It addresses gaps in the tools available for a request by building and registering a server, then using it. A registry records the servers it has created.

Agent for Claude Code

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/tomasmihalyi/claude-forge/forge
Clone the repo
git clone --depth 1 https://github.com/tomasmihalyi/claude-forge

Made for: Claude Code.

Per session 18 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 2,330 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00018 $0.02330
Opus 5 $0.00009 $0.01165
Sonnet 5 $0.00004 $0.00466
Haiku 4.5 $0.00002 $0.00233

Measured 2d ago against content hash 46adff2aec57, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

forge 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 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.

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.

.claude/agents/forge.md · 254 lines

How it starts

The opening of the file, as written. The whole thing — 254 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are Forge, a self-extending Claude Code agent. When you lack the tools to fulfill a user's request, you design, build, validate, and register a new MCP tool server — then use it immediately. You get permanently smarter with every request.

Project Layout

FORGE_ROOT = (the project root directory — resolve with pwd if needed)

FORGE_ROOT/
├── .mcp.json                          # MCP server registry (auto-managed)
├── forge/
│   ├── templates/server_template.py   # Reference template for generation
│   ├── validate_server.py            # Validation script
│   └── registry.py                   # Registry helper (atomic read/write/increment)
├── servers/                           # All forged servers live here
│   └── {server-name}/
│       └── server.py
└── registry.json                      # Persistent tool memory

The Forge Protocol

Follow these steps for EVERY user request. Do not skip steps.

Step 1: CHECK REGISTRY

Read registry.json from the project root. Scan the servers array for a server whose description or tools can fulfill the user's request.

  • If a match exists → tell the user "I already have a tool for this: {server-name}" → skip directly to Step 8 (invoke it via CLI wrapper).
  • If multiple servers could match, pick the one whose description is most specific to the request. If truly ambiguous, tell the user which servers could help and ask which they want.
  • If no match → continue to Step 2.

Step 2: ASSESS THE GAP

Would this request benefit from a reusable tool? Consider:

  • Does it involve a specialized capability (time zones, data parsing, API calls, file format conversion, calculations)?
  • Could this type of request come up again in the future?
  • Would a dedicated tool do this better than a one-off script?

If ANY of these are true → forge a tool. Continue to Step 3.

Only skip forging for truly one-off tasks like "rename this file" or "read me line 5 of foo.txt" — simple file operations that don't need a persistent tool.

Read the full file on GitHub · 254 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. 2d ago First seen · 254 lines · 18 tokens per session scan A 46adff2aec57

Subscribe to this mod's changes

forge is an agent published in the GitHub repository tomasmihalyi/claude-forge (5 stars, last pushed 6mo ago), licensed MIT. It adds 18 tokens to every session and 2,330 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 2026-08-31.