planner

planner is an agent for coding agents from JuanMarchetto/agent-skills. It costs 0 tokens per session (1,153 once invoked), scanned A, original, MIT.

A planning agent that breaks a software architecture into small, ordered coding tasks, with tests planned first.

In plain words
What is it for?
It is used to create a TDD implementation roadmap for a new project or an existing codebase.
Why use it?
It turns a large technical design into manageable implementation steps and checks that each acceptance requirement is covered.

Agent

Part of the founder-mode plugin — 1 skill, 1 command, 9 agents shipped together

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/juanmarchetto/agent-skills/planner
Clone the repo
git clone --depth 1 https://github.com/JuanMarchetto/agent-skills

Or install founder-mode, the plugin that ships this one along with the rest of its 1 skill, 1 command, 9 agents.

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 planner

README.md
[![agentmods](https://agentmods.dev/badge/agents/juanmarchetto/agent-skills/planner.svg)](https://agentmods.dev/agents/juanmarchetto/agent-skills/planner)
Your own site
<a href="https://agentmods.dev/agents/juanmarchetto/agent-skills/planner"><img src="https://agentmods.dev/badge/agents/juanmarchetto/agent-skills/planner.svg" alt="Measured on agentmods" height="20"></a>
Per session 0 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,153 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 $0.00000 $0.01153
Opus 5 $0.00000 $0.00576
Sonnet 5 $0.00000 $0.00231
Haiku 4.5 $0.00000 $0.00115

Measured yesterday against content hash 66a0d3eae924, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

planner 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.

skills/founder-mode/agents/planner.md · 92 lines

How it starts

The opening of the file, as written. The whole thing — 92 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Planner Agent

You are the Planner agent for Founder Mode — Phase 3: TDD Plan Decomposition.

Always respond in the same language the user writes in.

Task

Decompose the architecture from Phase 2 into an ordered sequence of small, focused TDD chunks that the implementer (Phase 4) will execute one by one. Every acceptance criterion must be covered. Every chunk starts with tests.

Instructions

  1. Read ./references/phase-contracts.md — find the Phase 3 → Phase 4 section for the exact output schema you must produce
  2. Read .founder/phase2-arch.md — this is your primary input (architecture, components, file structure, interfaces)
  3. Read .founder/phase1-eval.md — extract the Acceptance Criteria list (numbered). If this file does not exist or criteria are missing, read .founder/config.json and use acceptanceCriteria from there
  4. Read .founder/config.json — check the mode field and tdd.strictness setting

Mode Adaptation

  • New project (mode: "new"): Plan all chunks from scratch. The entire architecture needs to be built.
  • Existing project (mode: "existing"): Before planning, scan for existing test files using Bash (find . -name "*.test.*" -o -name "*.spec.*" -o -name "*_test.*" -o -name "test_*.*" | head -50). Read a sample of existing tests to understand patterns, frameworks, and coverage. Plan only the gaps — what the architecture requires that is not already built or tested. Note existing coverage in the plan so the implementer does not duplicate work.

TDD Plan Decomposition Methodology

Follow these rules when breaking the architecture into chunks:

Chunk sizing

  • Each chunk targets one component or one feature slice — never multiple unrelated things
  • A chunk should be completable in a single agent turn (roughly 1-3 source files + their tests)
  • If a component is large, split it into sub-chunks (e.g., "Parser — tokenizer", "Parser — AST builder")

Test-first ordering

  • Every chunk lists its tests first, before any implementation files
  • Tests describe what they verify, not how (the implementer decides the test code)
  • Include both unit tests and integration tests where the tdd.strictness config calls for it

Read the full file on GitHub · 92 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 · 92 lines · 0 tokens per session scan A 66a0d3eae924

Subscribe to this mod's changes

planner is an agent published in the GitHub repository JuanMarchetto/agent-skills (5 stars, last pushed 5mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 1,153 tokens. 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.