fmm

fmm is a skill for Claude Code, Codex from srobinson/fmm. It costs 96 tokens per session (7,236 once invoked), scanned A, original, MIT.

A code-navigation skill that uses a codebase index to find files, symbols, exports, and dependencies. It is intended for this specific codebase and replaces ordinary text searches for structural questions.

In plain words
What is it for?
Use it to find symbols, trace dependencies, inspect file structure, and assess the likely impact of a change.
Why use it?
It helps an agent locate definitions and understand how changes may affect other code before editing.

Skill for Claude CodeCodex

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/srobinson/fmm/templates
Any agent
npx skills add srobinson/fmm --skill templates
Clone the repo
git clone --depth 1 https://github.com/srobinson/fmm

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 fmm

README.md
[![agentmods](https://agentmods.dev/badge/skills/srobinson/fmm/templates.svg)](https://agentmods.dev/skills/srobinson/fmm/templates)
Your own site
<a href="https://agentmods.dev/skills/srobinson/fmm/templates"><img src="https://agentmods.dev/badge/skills/srobinson/fmm/templates.svg" alt="Measured on agentmods" height="20"></a>
Per session 96 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 7,236 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 $0.00096 $0.07236
Opus 5 $0.00048 $0.03618
Sonnet 5 $0.00019 $0.01447
Haiku 4.5 $0.00010 $0.00724

Measured 4d ago against content hash ccb46ad0728d, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

fmm 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 4d 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.

crates/fmm-cli/templates/SKILL.md · 408 lines

How it starts

The opening of the file, as written. The whole thing — 408 lines — stays where its author put it; the contents beside it link to each section on GitHub.

FMM — MCP-First Code Navigation

This codebase has FMM metadata available via the fmm MCP server. All tools are prefixed fmm_*. Use them for instant, structured lookups instead of grep/read.

The index stays current throughout your session — a hook re-indexes any file you edit immediately after the write. You can trust fmm data at every point in your task.

Before You Touch Any Code

If you are about to call Read, Grep, or Glob on a source file — stop. Ask: does fmm answer this? It answers structural questions at O(1): file topology, symbol locations, export maps, dependency graphs, blast radius. Reading files to derive those answers costs 10-50x more tokens and is less complete.

Reserve Read for two cases only: editing a specific symbol, or understanding logic that fmm_read_symbol cannot provide.

MCP Tools (ALWAYS USE THESE FIRST)

Tool Use Case Example
fmm_list_files Orient in an unknown codebase. sort_by: loc (heaviest), downstream (most-imported, best pre-refactoring), name, exports, modified fmm_list_files(directory: "src/", sort_by: "downstream")
fmm_file_outline Full structural profile — exports, public/private (include_private) methods, line ranges fmm_file_outline(file: "src/core/index.ts", include_private: true)
fmm_lookup_export O(1) exact lookup → file, line range, full file profile fmm_lookup_export(name: "createPipeline")
fmm_list_exports Export search: substring or regex (auto-detected). ^handle, Service$, ^[A-Z] for regex; plain text for substring fmm_list_exports(pattern: "^[A-Z]", directory: "packages/core/")
fmm_read_symbol Exact source for a named export or specific method fmm_read_symbol(name: "Injector.loadInstance")
fmm_search Cross-cutting queries: imports, LOC range, depends_on, term fmm_search(imports: "rxjs", min_loc: 500)
fmm_dependency_graph Upstream deps + downstream blast radius. filter: "source" strips test files, filter: "tests" shows only test coverage fmm_dependency_graph(file: "src/core/index.ts", filter: "source")
fmm_glossary Symbol impact — call-site callers or test coverage by method fmm_glossary(pattern: "Injector.loadInstance", mode: "source")

Read the full file on GitHub · 408 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. 4d ago First seen · 408 lines · 96 tokens per session scan A ccb46ad0728d

Subscribe to this mod's changes

fmm is a skill published in the GitHub repository srobinson/fmm (2 stars, last pushed 2mo ago), licensed MIT. It adds 96 tokens to every session and 7,236 once invoked, about $0.0005 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.

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