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Agent skill

Counterfact Generator Internals

by counterfact in counterfact/api-simulator

Modify TypeScript generator internals, OpenAPI parsing/schema handling, and generated file writing behavior without regressing regeneration guarantees.

MITAuto-check passedBackend & APIs

Install Counterfact Generator Internals

skills CLI
$ npx skills add counterfact/api-simulator --skill counterfact-generator-internals -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install counterfact/api-simulator counterfact-generator-internals --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/counterfact/api-simulator.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.github/skills/counterfact-generator-internals .claude/skills/counterfact-generator-internals && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
counterfact-generator-internals
GitHub stars
170
Token cost
~648 tokens
SKILL.md length
199 words
Files
1
Skills in repo
12
Repo updated
First seen
Licence
MIT

At a glance

Modify TypeScript generator internals, OpenAPI parsing/schema handling, and generated file writing behavior without regressing regeneration guarantees.

  • Tasks that involve OpenAPI specifications
  • SKILL.md covers When to use this skill, Files to inspect first, Existing conventions to follow and Common mistakes to avoid, plus 1 more section
  • Calls yarn

What it does

Counterfact Generator Internals is an agent skill from counterfact/api-simulator. Modify TypeScript generator internals, OpenAPI parsing/schema handling, and generated file writing behavior without regressing regeneration guarantees.

Its SKILL.md is about 650 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Backend & APIs, covering OpenAPI specifications. It works with OpenAPI and TypeScript. The repository describes itself as: Turn an OpenAPI spec into a local API in one command. Build and test your frontend with custom responses, shared state, and simulated failures, without waiting for the backend. The licence is MIT.

When your agent uses it

  • Tasks that involve OpenAPI specifications

Example prompts

  • “/counterfact-generator-internals”

What it can do on your machine

Read from SKILL.md and the folder at commit fc1c7f8. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Shell commands in SKILL.md call:

    • yarn

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md. Its commands use yarn, which can reach the network depending on how they are called.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Counterfact Generator Internals loads about 648 tokens when it runs. Until then it costs about 46 tokens; SKILL.md has 199 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~46
When it runs · the whole SKILL.md, loaded when a task matches
~648

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from counterfact/api-simulator at commit fc1c7f8, republished under its MIT licence (© counterfact). 199 words, ~648 tokens.

Download SKILL.mdSave it as .claude/skills/counterfact-generator-internals/SKILL.md (or your agent's skills folder).
name
counterfact-generator-internals
description
Modify TypeScript generator internals, OpenAPI parsing/schema handling, and generated file writing behavior without regressing regeneration guarantees.
applyTo
packages/counterfact/src/typescript-generator/**/*.ts, packages/counterfact/src/server/openapi-document.ts…

Counterfact Generator Internals Skill

When to use this skill

Use this skill when changing OpenAPI loading/bundling, schema-to-type generation, operation/type coders, repository/script writing, or generated versions typing.

Files to inspect first

  • packages/counterfact/src/typescript-generator/README.md
  • packages/counterfact/src/typescript-generator/code-generator.ts
  • packages/counterfact/src/typescript-generator/specification.ts
  • packages/counterfact/src/typescript-generator/requirement.ts
  • packages/counterfact/src/typescript-generator/repository.ts
  • packages/counterfact/src/typescript-generator/schema-type-coder.ts

Existing conventions to follow

  • Keep the generator architecture layered: Specification/Requirement -> coders -> Script -> Repository.
  • Preserve regeneration contract: existing route files are not overwritten; generated types are overwritten.
  • Support OpenAPI features through typed coders and requirement traversal rather than ad-hoc string logic.
  • Keep generated output deterministic and formatted via existing script/repository pipeline.
  • Build generator watch sets through @counterfact/openapi source classification: watch every unique local contributing input (base document plus overlays), exclude remote inputs and _, and regenerate from the complete ordered input set after any change. Do not infer URL-ness from a string prefix.

Common mistakes to avoid

  • Overwriting user-edited route files in Repository.writeFiles.
  • Implementing new OpenAPI behavior in only one coder path (missing runtime/type parity).
  • Skipping fixture/snapshot updates for changed generated output.
  • Breaking group/versioned output conventions (types/versions.ts per group).

How to validate the change

  • Run: yarn lint, yarn build, yarn test.
  • Run focused generator tests first (affected coder + integration/snapshot tests in packages/counterfact/test/typescript-generator/).
  • If behavior changes for generated artifacts, verify snapshots and relevant docs (packages/counterfact/docs/reference.md, packages/counterfact/docs/faq.md).

© counterfact, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in .github/skills/counterfact-generator-internals of counterfact/api-simulator.

Open the folder on GitHubat commit fc1c7f8

Compare with similar skills

Counterfact Generator Internals next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Counterfact Generator Internals compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Counterfact Generator Internals this skillcounterfact/api-simulator170—~648Automated safety check: PassMIT
OpenAPI to MCP Servermcp-use/mcp-use11k—~5.2kAutomated safety check: PassApache-2.0
Api2clialexknowshtml/api2cli454—~2.9kAutomated safety check: PassMIT
Projectsamchon/nestia2.2k—~3kAutomated safety check: PassMIT
API ContractChenyCHENYU/Robot_Admin1k—~1.9kAutomated safety check: PassMIT
Typescriptscalar/scalar16k—~1.1kAutomated safety check: PassMIT

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More from counterfact/api-simulator

All 12 skills in this repo

  • Counterfact PR Creation

    counterfact/api-simulator

    Create Counterfact pull requests with the required agent-authored acceptance and repository-learning notes; do not use to review another PR.

    170 GitHub stars~918 tokensUpdated today
    Auto-check passed

  • Counterfact Repl

    counterfact/api-simulator

    Interact with Counterfact mock API server programmatically. An agent skill from counterfact/api-simulator.

    170 GitHub stars~3.2k tokensUpdated today
    Auto-check passed

  • Build Simulation

    counterfact/api-simulator

    Build a fully simulated API from an OpenAPI spec using Counterfact.

    170 GitHub stars~2.9k tokensUpdated today
    Auto-check passed

  • Counterfact Maintenance

    counterfact/api-simulator

    Keep contributor changes aligned with repository test patterns, diagnostics, black-box test boundaries, release/versioning workflow, documentation requirements, and compatibility.

    170 GitHub stars~3.1k tokensUpdated today
    Auto-check passed

  • Counterfact Repo Basics

    counterfact/api-simulator

    Provide Counterfact repository orientation, high-level architecture, and the canonical command reference for install/build/test/lint workflows.

    170 GitHub stars~868 tokensUpdated today
    Auto-check passed

  • Route

    counterfact/api-simulator

    Edit Counterfact route files to add endpoint behavior while keeping handlers thin and delegating business logic to context classes.

    170 GitHub stars~341 tokensUpdated today
    Auto-check passed

Works with

Categories

Questions about Counterfact Generator Internals

What does Counterfact Generator Internals do?

Modify TypeScript generator internals, OpenAPI parsing/schema handling, and generated file writing behavior without regressing regeneration guarantees. Counterfact Generator Internals is an agent skill from counterfact/api-simulator. Modify TypeScript generator internals, OpenAPI parsing/schema handling, and generated file writing behavior without regressing regeneration guarantees.

When should I use Counterfact Generator Internals?

Counterfact Generator Internals fits situations like: tasks that involve OpenAPI specifications.

How do I install Counterfact Generator Internals in Claude Code?

Run `npx skills add counterfact/api-simulator --skill counterfact-generator-internals -a claude-code`. Or copy the skill folder (.github/skills/counterfact-generator-internals in counterfact/api-simulator) into .claude/skills/counterfact-generator-internals in your project. Claude Code loads it when a task matches its description.

How do I install Counterfact Generator Internals in Codex?

Run `npx skills add counterfact/api-simulator --skill counterfact-generator-internals -a codex`. Or copy the skill folder (.github/skills/counterfact-generator-internals in counterfact/api-simulator) into .agents/skills/counterfact-generator-internals in your project. Codex loads it when a task matches its description.

Can I use Counterfact Generator Internals in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add counterfact/api-simulator --skill counterfact-generator-internals -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/counterfact-generator-internals, .gemini/skills/counterfact-generator-internals, .github/skills/counterfact-generator-internals and .opencode/skills/counterfact-generator-internals in your project.

What does Counterfact Generator Internals need to run?

Going by SKILL.md and its folder, Counterfact Generator Internals needs the command-line tools its instructions call (yarn).

Does Counterfact Generator Internals access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Counterfact Generator Internals safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Counterfact Generator Internals use?

Counterfact Generator Internals is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Counterfact Generator Internals use?

About 648 tokens (SKILL.md is roughly 2.6k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Counterfact Generator Internals?

Skills that share tags, products or a category with Counterfact Generator Internals: OpenAPI to MCP Server (mcp-use/mcp-use, 11k stars), Api2cli (alexknowshtml/api2cli, 454 stars), Project (samchon/nestia, 2.2k stars) and API Contract (ChenyCHENYU/Robot_Admin, 1k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Counterfact Generator Internals?

counterfact (a GitHub organization) maintains it in counterfact/api-simulator, which has 170 GitHub stars. The repository holds 12 skills in this directory. The repository was last updated on October 10, 2026.

Source: counterfact/api-simulator on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.