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.
npx skills add lukas-grigis/ralphctl --skill ralphctl-api-and-interface-designgit clone --depth 1 https://github.com/lukas-grigis/ralphctlWrote 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.
[](https://agentmods.dev/skills/lukas-grigis/ralphctl/ralphctl-api-and-interface-design)<a href="https://agentmods.dev/skills/lukas-grigis/ralphctl/ralphctl-api-and-interface-design"><img src="https://agentmods.dev/badge/skills/lukas-grigis/ralphctl/ralphctl-api-and-interface-design/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.
<a href="https://agentmods.dev/skills/lukas-grigis/ralphctl/ralphctl-api-and-interface-design"><img src="https://agentmods.dev/badge/skills/lukas-grigis/ralphctl/ralphctl-api-and-interface-design.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00100 | $0.01461 |
| Opus 5.5 | $0.00040 | $0.00584 |
| Sonnet 5.5 | $0.00020 | $0.00292 |
| Haiku 4.5 | $0.00010 | $0.00146 |
Grade A, and why
ralphctl-api-and-interface-design 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.
How it starts
The opening of the file, as written. The whole thing — 118 lines — stays where its author put it; the contents beside it link to each section on GitHub.
API and Interface Design
Adapted from addyosmani/agent-skills — "API and Interface Design" (MIT). Adapted for ralphctl's harness contract.
Good interfaces make the right use easy and the wrong use hard. This applies to every surface where one piece of code talks to another: a network API, a library's exports, a module boundary inside one repository, a CLI's flags and exit codes, a file or message format. The guidance is language-neutral — express it in the project's own idiom and with its own typing or schema mechanism.
When this applies
- Plan — when a ticket adds or changes an interface, make the contract its own task or the first step of one, and put its shape in the verification criteria: inputs, outputs, error cases, and what existing consumers must keep seeing. Name who consumes the interface today.
- Execute — define the contract before the body, and check every change to an existing interface against its current consumers before making it. When reviewing, a breaking change the task did not ask for is a finding even when the new code is correct.
Every observable behaviour is a commitment
Hyrum's law: with enough consumers, everything observable gets depended on — field order, error message text, default values, timing, undocumented quirks. So:
- Expose deliberately. Anything a caller can observe is something you may have to keep.
- Keep implementation details out of the interface — storage ids, internal layout, stack traces in errors.
- Tests are necessary but not sufficient: a "safe" change still breaks a consumer that relies on behaviour no test pins. Search for real consumers before changing what they can see.
Core principles
Contract first
Write the interface — names, input and output shapes, error cases, invariants — before the implementation. The contract is the spec; the body follows it. Separate what a caller provides from what the system returns: generated fields (ids, timestamps) appear only in the output shape.
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.
- yesterday First seen · 118 lines · 100 tokens per session scan A d8c7200ee113
ralphctl-api-and-interface-design is a skill published in the GitHub repository lukas-grigis/ralphctl (24 stars, last pushed today), licensed MIT. It adds 100 tokens to every session and 1,461 once invoked, about $0.0004 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 2026-10-18.
Other skills, from other repositories
llm-provider
Adds a new LLM provider implementing LLMProvider interface with call() and stream() methods. Integrates with provider factory in src/llm/index.ts, config detection in src/llm/config.ts, and error handling via tracking and recovery. Use when adding a new model backend, integrating a third-party LLM API, or extending…
tech-design
A guided process for writing a backend technical design from a product requirements document or feature description. A technical design explains how a feature should work in code and services.
api-interface-design
Use when designing public APIs, module boundaries, provider adapters, tool schemas, or data contracts.
plugin-system
Generic plugin system for Python applications. Auto-discovery, validation, fault tolerance. Zero dependencies (Python stdlib only).
codegen
Use for .NET code generation work with Roslyn, Microsoft.OpenApi, Razor templates, DTO/manager/controller generation, REST API generation, C# HttpClient generation, Angular/Axios TypeScript request clients, generated formatting, and deterministic output.
serve
Wire a compiled rote pipeline up as an MCP tool so Claude can trigger the deployed workflow directly. Use when the user says "register my compiled pipeline", "serve my pipelines over MCP", "trigger the workflow from Claude", "hook the pipeline up to Claude", or asks what to do after rote compile and deployment. Covers…