sdd-check

sdd-check is a skill for Claude Code from viamus/claude-sdd-plugin. It costs 39 tokens per session (773 once invoked), scanned A, original, MIT.

A checker that compares generated implementation code with its approved SDD specification. It examines inputs, outputs, business rules, and other stated requirements to find differences.

In plain words
What is it for?
Use it to verify one specification, several specifications, or all approved specifications that have generated code.
Why use it?
It catches drift introduced when code is changed manually after generation. This helps reveal when the implementation no longer matches the agreed specification.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter.

Part of the sdd plugin — 8 skills shipped together

Good fit Use it to verify one specification, several specifications, or all approved specifications that have generated code.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/viamus/claude-sdd-plugin/sdd-check
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.

Any agent
npx skills add viamus/claude-sdd-plugin --skill sdd-check
Clone the repo
git clone --depth 1 https://github.com/viamus/claude-sdd-plugin

Made for: Claude Code.

Or install sdd, the plugin that ships this one along with the rest of its 8 skills.

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-check

README.md
[![agentmods](https://agentmods.dev/badge/skills/viamus/claude-sdd-plugin/sdd-check/github.svg)](https://agentmods.dev/skills/viamus/claude-sdd-plugin/sdd-check)
Your own site
<a href="https://agentmods.dev/skills/viamus/claude-sdd-plugin/sdd-check"><img src="https://agentmods.dev/badge/skills/viamus/claude-sdd-plugin/sdd-check/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-check

Your own site · 80×15
<a href="https://agentmods.dev/skills/viamus/claude-sdd-plugin/sdd-check"><img src="https://agentmods.dev/badge/skills/viamus/claude-sdd-plugin/sdd-check.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 39 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 773 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 $0.00039 $0.00773
Opus 5.5 $0.00016 $0.00309
Sonnet 5.5 $0.00008 $0.00155
Haiku 4.5 $0.00004 $0.00077

Measured 1mo ago against content hash 5b4d1e1c9cd9, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

sdd-check 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 1mo 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.

skills/sdd-check/SKILL.md · 81 lines

How it starts

The opening of the file, as written. The whole thing — 81 lines — stays where its author put it; the contents beside it link to each section on GitHub.

SDD Check — Consistency Verification

You are the SDD Orchestrator verifying that implementation code is consistent with its specification.

Instructions

  1. Determine which specs to check:

    • If $ARGUMENTS contains --all: check ALL approved specs with output_files
    • If $ARGUMENTS is provided (one or more paths): use each one
    • If no arguments: search specs/ for files with status: approved that have output_files defined
      • If multiple found, ask: "Found X specs with generated code. Check all, or pick specific ones?"
    • If none found, say: "No specs with generated code found."
    • For multiple specs, process each one and generate a unified summary at the end
  2. Read the spec file completely

  3. Read the output_files listed in the spec frontmatter

    • If output_files is empty, try to find related code by matching file names against the spec name
  4. Perform consistency checks:

Check Matrix

# Check How to Verify
1 Interface Match Input types in code match spec's Inputs table
2 Output Match Return types in code match spec's Outputs table
3 Business Rules Each numbered rule in spec has corresponding logic in code
4 Error Handling Each error scenario in spec has a corresponding catch/throw/return
5 No Extra Features Code doesn't implement functionality not in the spec
6 Dependencies Used Libraries listed in spec are the ones used in code
  1. Generate consistency report:
## 🔍 SDD Consistency Report: {spec-name}

**Spec:** specs/{name}.spec.md
**Code:** {list of code files}

### Results

| # | Check | Status | Details |
|---|-------|--------|---------|
| 1 | Interface Match | ✅/❌ | ... |
| 2 | Output Match | ✅/❌ | ... |
| 3 | Business Rules | ✅/❌ | X/Y rules implemented |
| 4 | Error Handling | ✅/❌ | X/Y scenarios covered |
| 5 | No Extra Features | ✅/⚠️ | ... |
| 6 | Dependencies | ✅/❌ | ... |

### Divergences Found
<!-- List specific mismatches -->

### Recommendations
<!-- For each divergence, suggest: fix code OR update spec -->

Read the full file on GitHub · 81 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. 1mo ago First seen · 81 lines · 39 tokens per session scan A 5b4d1e1c9cd9

Subscribe to this mod's changes

sdd-check is a skill published in the GitHub repository viamus/claude-sdd-plugin (4 stars, last pushed 6mo ago), licensed MIT. It adds 39 tokens to every session and 773 once invoked, about $0.0002 per session on Opus 5.5. 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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