sdd-plan

sdd-plan is a command for Claude Code from niels-emmer/myace. It costs 25 tokens per session (413 once invoked), scanned A, original, MIT.

A command that turns an agreed feature specification into a technical design covering architecture, data, and interfaces.

In plain words
What is it for?
Use it to document the chosen approach, data model, APIs or function interfaces, edge cases, and rejected alternatives.
Why use it?
It prevents teams from starting implementation with unresolved design choices or plans that do not cover the requirements.

Command for Claude Code

Written for Claude Code: a Claude Code command (commands/*.md). Also seen: mentions Codex; built for aider; mentions OpenCode.

Good fit Use it to document the chosen approach, data model, APIs or function interfaces, edge cases, and rejected alternatives.

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Install with agentmods
npx agentmods add commands/niels-emmer/myace/sdd-plan
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.

Clone the repo
git clone --depth 1 https://github.com/niels-emmer/myace

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 sdd-plan

README.md
[![agentmods](https://agentmods.dev/badge/commands/niels-emmer/myace/sdd-plan/github.svg)](https://agentmods.dev/commands/niels-emmer/myace/sdd-plan)
Your own site
<a href="https://agentmods.dev/commands/niels-emmer/myace/sdd-plan"><img src="https://agentmods.dev/badge/commands/niels-emmer/myace/sdd-plan/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 sdd-plan

Your own site · 80×15
<a href="https://agentmods.dev/commands/niels-emmer/myace/sdd-plan"><img src="https://agentmods.dev/badge/commands/niels-emmer/myace/sdd-plan.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 25 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 413 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.
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 $0.00025 $0.00413
Opus 5 $0.00013 $0.00206
Sonnet 5 $0.00005 $0.00083
Haiku 4.5 $0.00003 $0.00041

Measured 5d ago against content hash a78580103b5e, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-09, from the pricing page.

Security

Grade A, and why

sdd-plan 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 5d 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.

collections/additional/spec-driven-dev/commands/sdd-plan.md · 14 lines

What it actually says

  1. Read docs/specs/<slug>/spec.md. If it still has unresolved [NEEDS CLARIFICATION] markers, stop and run sdd-clarify first — planning against an ambiguous spec just moves the ambiguity into the code.
  2. Resolve open technical unknowns explicitly before designing around them: which library, which existing service boundary, which of two viable data shapes. Where the codebase already has an established pattern for something similar, follow it rather than introducing a second way to do the same thing.
  3. If the architecture-review skill is available (from the Software Engineer collection), use its design-note discipline for this step — a new data model, service boundary, or auth-relevant change is exactly the kind of decision that skill exists to force onto paper before code.
  4. Write docs/specs/<slug>/plan.md covering: the chosen approach and why alternatives were rejected, the data model (new/changed entities and their relationships), the interfaces being added or changed (API endpoints, function signatures, event shapes), and how this plan satisfies every functional requirement and edge case listed in the spec.
  5. Cross-check against docs/constitution.md if it exists — a plan that violates a stated principle needs either a redesign or an explicit, justified exception noted in the plan, not a silent violation.
  6. Do not write task lists or code here — that's sdd-tasks and sdd-implement. This step produces the design that both build on.
  7. Report the plan's location and flag anything you're genuinely uncertain about rather than presenting a guess as a settled decision.
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. 5d ago First seen · 14 lines · 25 tokens per session scan A a78580103b5e

Subscribe to this mod's changes

sdd-plan is a command published in the GitHub repository niels-emmer/myace (1 stars, last pushed 2d ago), licensed MIT. It adds 25 tokens to every session and 413 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.