design-spec-expert

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 jggomez/expert-ai-developer-skills --skill design-spec-expert

Clone the repo

git clone --depth 1 https://github.com/jggomez/expert-ai-developer-skills

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/jggomez/expert-ai-developer-skills/design-spec-expert/github.svg)](https://agentmods.dev/skills/jggomez/expert-ai-developer-skills/design-spec-expert)

Your own site

<a href="https://agentmods.dev/skills/jggomez/expert-ai-developer-skills/design-spec-expert"><img src="https://agentmods.dev/badge/skills/jggomez/expert-ai-developer-skills/design-spec-expert/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/jggomez/expert-ai-developer-skills/design-spec-expert"><img src="https://agentmods.dev/badge/skills/jggomez/expert-ai-developer-skills/design-spec-expert.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 46 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 920 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.

Model	Per session	Once invoked
Fable 5.1	$0.00046	$0.00920
Opus 5.5	$0.00018	$0.00368
Sonnet 5.5	$0.00009	$0.00184
Haiku 4.5	$0.00005	$0.00092

Measured today against content hash 1dec16c284a8, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

design-spec-expert 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 today.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/create_sdd.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

plugins/antigravity/python-backend/skills/design-spec-expert/SKILL.md · 52 lines

How it starts

The opening of the file, as written. The whole thing — 52 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Design Spec Expert Skill

Overview

Design Spec Expert formalizes backend services, database schema deltas, and REST/GraphQL/gRPC contracts into a concise Backend / API Design Spec (docs/<feature-name>/api-spec.md or SDD <= 70 lines) before implementation—eliminating verbose boilerplate while preventing contract drift across Claude Code and Google Antigravity.

When to Use

Trigger Scenarios

Introducing new API endpoints, request/response contracts, or cross-service integrations.
Designing new database tables, migrations, indexes, or async worker pipelines.

When NOT to Use

Changes following existing endpoints/models: SKIP SDD/api-spec.md creation completely when changes fit established routes, schemas, or localized Tier 1 bugfixes/refactors.
Single architectural pattern trade-off: Use senior-architect-engineering for a concise MADR (<= 55 lines).
Product user stories: Use product-analyst (## Product in docs/<feature-name>/spec.md, <= 50 lines).

Process

Check Capability Gate & Context: Inspect root AGENTS.md (<= 90 lines wired to context/memory/MEMORY.md) and existing routers/models. If the task reuses existing endpoints and models, skip SDD authoring and proceed to TDD.
Scaffold & Author Concise Spec (<= 70 lines): Run create_sdd.py or write docs/<feature-name>/api-spec.md directly following references/sdd-template.md across 4 crisp sections:
- ## 1. Objective & Scope: Concrete problem/SLA + explicit In Scope / Out of Scope bullets.
- ## 2. Architecture & Data Model: Compact Mermaid flow + exact table/column/index migration delta.
- ## 3. API Endpoints & Contracts: Compact table (Method & Path | Request schema | Response schema | Status codes).
- ## 4. Security, Edge Cases & Trade-offs: AuthN/AuthZ, rate/input validation, idempotency/retries, and + Pros / - Risks.
Gate Sign-off: Align contracts with stakeholders (ask_question in Tier 2/3) and mark status Approved before delegating to code-implementer.

Read the full file on GitHub · 52 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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.

today First seen · 52 lines · 46 tokens per session scan A 1dec16c284a8

Subscribe to this mod's changes

design-spec-expert is a skill published in the GitHub repository jggomez/expert-ai-developer-skills (30 stars, last pushed yesterday), licensed Apache-2.0. It adds 46 tokens to every session and 920 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 2026-11-06.

Backend and APIs Planning Writing and docs

design-spec-expert next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
design-spec-expertjggomez/expert-ai-developer-skills	Skill	30	yesterday	Apache-2.0	A	46	Claude Code, Codex
mem0-oss-to-platformmem0ai/mem0	Skill	68k	2d ago	Apache-2.0	A	217	Claude Code, Codex
azure-mgmt-botservice-dotnetmicrosoft/skills	Skill	3.2k	yesterday	MIT	A	78	Claude Code
fastapi-router-pymicrosoft/skills	Skill	3.2k	yesterday	MIT	A	46	Claude Code
dev-runtimelangwatch/langwatch	Skill	5.0k	yesterday	Apache-2.0	A	172	Claude Code
api-designericrisco/rsc-harness	Skill	503	2d ago	MIT	A	105	Claude Code, Codex
migrate-segw-to-raparc-mcp/arc-1	Skill	252	yesterday	MIT	A	106	Claude Code