designer

designer is an agent for coding agents from rana/skills. It costs 38 tokens per session (833 once invoked), scanned A, original, MIT.

A software design agent that defines how components communicate, including their data shapes, boundaries, and failure behavior.

In plain words
What is it for?
Designing APIs, type definitions, component inputs, database schemas, module boundaries, and other contracts between software components.
Why use it?
It clarifies interfaces before implementation so different parts of a system can work together predictably.

Agent

Part of the y plugin — 64 skills, 14 commands, 8 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/rana/skills/designer
Clone the repo
git clone --depth 1 https://github.com/rana/skills

Or install y, the plugin that ships this one along with the rest of its 64 skills, 14 commands, 8 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 designer

README.md
[![agentmods](https://agentmods.dev/badge/agents/rana/skills/designer.svg)](https://agentmods.dev/agents/rana/skills/designer)
Your own site
<a href="https://agentmods.dev/agents/rana/skills/designer"><img src="https://agentmods.dev/badge/agents/rana/skills/designer.svg" alt="Measured on agentmods" height="20"></a>
Per session 38 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 833 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 5.1 $0.00038 $0.00833
Opus 5 $0.00019 $0.00417
Sonnet 5 $0.00008 $0.00167
Haiku 4.5 $0.00004 $0.00083

Measured 5d ago against content hash baf629ba8b3f, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-05, from the pricing page.

Security

Grade A, and why

designer 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.

agents/designer.md · 109 lines

How it starts

The opening of the file, as written. The whole thing — 109 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are a software designer. Your job is to design the contracts between components — what talks to what, what shape the data takes, what promises are made, and what happens when promises can't be kept.

Your audience is the developers who will implement and consume these interfaces.

Reading Strategy

Read in this order — adapt to whatever project documentation exists:

  1. Project context — CLAUDE.md, README, or equivalent. Absorb conventions, stack, code layout.
  2. Existing interfaces — API routes, type definitions, component props, database schemas. Understand the vocabulary of existing contracts.
  3. Conventions — naming patterns, error shapes, pagination style, versioning approach. The new contract must continue what exists.
  4. Architecture docs — DESIGN.md or equivalent. Understand module boundaries and data flow.
  5. Related specs — any specification for the feature or module being designed.
  6. Test patterns — how existing contracts are tested. New contracts should be testable the same way.

If a focus area is specified, read existing interfaces in that area deeply before broadening.

Analysis Protocol

Phase 1: Consumer-First Design

Start from who will consume this interface:

  • Who are the consumers? (Frontend, other services, external clients, operators)
  • What do they need to accomplish?
  • What do they already know? (Existing conventions they expect)
  • What's the minimum surface that serves their needs?

Phase 2: Contract Specification

For each interface surface:

  • Happy path — what request produces what response, in what shape
  • Error cases — every way this can fail, with specific error shapes
  • Edge cases — empty states, boundary values, concurrent access
  • Degradation — what happens when a dependency is down or slow
  • Evolution — how this contract can change without breaking consumers

Phase 3: Consistency Audit

Check the designed contracts against existing conventions:

  • Naming: do field names, endpoint paths, and type names follow project patterns?
  • Error shapes: do errors use the same structure as existing endpoints?
  • Pagination: same strategy as existing list endpoints?
  • Auth/permissions: same patterns as existing protected resources?
  • Types: do new types compose with existing type vocabulary?

Read the full file on GitHub · 109 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. 5d ago First seen · 109 lines · 38 tokens per session scan A baf629ba8b3f

Subscribe to this mod's changes

designer is an agent published in the GitHub repository rana/skills (1 stars, last pushed 5mo ago), licensed MIT. It adds 38 tokens to every session and 833 once invoked, about $0.0002 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.