Mock
Designs mock servers and consumer-driven contract tests (Pact/Prism/WireMock/msw) so teams can build without depending on the live API. Use when parallelizing frontend and backend development or establishing contract testing in CI. Trigger with \"set up API mocks\", \"design contract tests\".
- Type
- Subagent
- Repository
- jeremylongshore/tons-of-skills-marketplace
- GitHub stars
- 2.8k
- License
- MIT
- Repo last updated
- Sep 27, 2026
- Source file
- plugins/ai-agency/tonone/agents/mock.md
- Model
- sonnet
- Version
- 1.0.0
- Author
- Jeremy Longshore <[email protected]>
What Mock is
Mock is a subagent published in the jeremylongshore/tons-of-skills-marketplace repository on GitHub, which has about 2.8k stars. The repository describes itself as: “Model-agnostic agent-skills platform with a harness-free canonical layer, verified adapters, and the ccpi package manager. Explore at tonsofskills.com.”
A subagent is a specialist assistant that Claude can hand part of a task to. It is a markdown file whose frontmatter sets a name, a description that tells Claude when to delegate, and optionally the tools and model it may use; the body becomes the subagent's own system prompt.
Because a subagent works in its own context, it keeps the main conversation focused: Claude can send a narrow job, such as a review or a specialised analysis, to Mock and get back a compact result.
How to install Mock
Claude Code
- Download mock.md from the repository.
- Save it to ~/.claude/agents/ to use it in every project, or to .claude/agents/ inside one project to share it through version control.
- Claude Code watches these folders, so the subagent is usually available right away. Ask Claude to use it by name, or @-mention it to make sure it runs.
Claude Cowork
- Cowork loads subagents through plugins. If the repository is packaged as a plugin marketplace, add it under Customize → Plugins → Add marketplace and install the plugin that contains this subagent.
- Otherwise, bundle the file into your own plugin's agents/ folder and upload it from Customize → Plugins.
New to extending Cowork? Our plugins guide and Customize guide explain how skills, plugins, and connectors fit together.
Inside the source file
An excerpt from plugins/ai-agency/tonone/agents/mock.md, shared under the repository's MIT license. Read the full file on GitHub.
You are Mock — API Mocking & Contract Engineer on the Developer Experience Team. Designs mock servers and contract tests that let developers build without depending on the real API.
Think in developer empathy and time-to-value. Every friction point in the developer experience is a drop-off. Every missing doc is a support ticket. Every breaking change without a migration guide is a churned integration.
Communication
Respond terse. All technical substance stays — only filler dies. Follow output-kit protocol: compressed prose, no filler, fragments OK. Documents: normal prose. See docs/output-kit.md for CLI skeleton, severity indicators, 40-line rule.
Operating Principle
A mock is a contract made executable. Consumer-driven contract testing (Pact) catches breaking changes before they reach production. A mock server lets frontend and mobile teams build in parallel with the backend. The mock must faithfully represent the API contract — a mock that diverges from reality is worse than no mock because it breeds false confidence.
What you skip: Integration testing against the real API — that's Proof. Mock handles the simulation layer.
What you never skip: Never let a mock diverge from the real API contract without detection. Never mock an endpoint without its error responses. Never use a mock in a test without a plan to validate against the real API.
Scope
Owns: Mock server design, consumer-driven contract testing, API simulation, test fixture design
Skills
- Mock Design: Design a mock server for an API — tooling selection, response fixtures, and error scenarios.
- Mock Contract: Design a consumer-driven contract testing setup — Pact configuration and CI integration.
- Mock Recon: Audit existing mocks and test doubles — find contract drift, missing error cases, and stale fixtures.
Key Rules
- Consumer-driven contracts: Pact for REST; gRPC has built-in reflection for mocking
- Mock tools: Prism (OpenAPI-native), WireMock (flexible), msw (browser/Node), nock (Node HTTP)
- Error responses: mock must include all documented error codes, not just 200
- Contract drift: CI check that mock contract matches current OpenAPI spec on every PR
- Seeded data: mock responses use realistic data (Faker), not 'string' and '123'
Process Disciplines
When performing Mock work, follow these superpowers process skills:
Iron rule: No completion claims without fresh verification.
Before you install
- Read the whole file first. Skills, commands, and subagents are instructions Claude will follow, so make sure they match what you want.
- Check which tools, scripts, or MCP servers it uses. Local servers and scripts run with your permissions.
- Try it in a test project or a copy of your files before pointing it at real work.
- Pin the version you tested, and review changes before updating.
- Watch for instructions that fetch web content or run shell commands; those are where prompt injection risks start. See our prompt injection guide.
FAQ
What is Mock?
Mock is a subagent for Claude Code and Claude Cowork from the jeremylongshore/tons-of-skills-marketplace repository on GitHub. Designs mock servers and consumer-driven contract tests (Pact/Prism/WireMock/msw) so teams can build without depending on the live API. Use when parallelizing frontend and backend development or establishing contract testing in CI. Trigger with \"set up API mocks\", \"design contract tests\".
How do I install Mock in Claude Code?
Download mock.md from the repository. Save it to ~/.claude/agents/ to use it in every project, or to .claude/agents/ inside one project to share it through version control. Claude Code watches these folders, so the subagent is usually available right away. Ask Claude to use it by name, or @-mention it to make sure it runs.
Can I use Mock in Claude Cowork?
Cowork loads subagents through plugins. If the repository is packaged as a plugin marketplace, add it under Customize → Plugins → Add marketplace and install the plugin that contains this subagent. Otherwise, bundle the file into your own plugin's agents/ folder and upload it from Customize → Plugins.
Is Mock safe to install?
It is a third-party community resource, not reviewed by Anthropic or this site. Read the source file first, check which tools and connectors it uses, and install only from sources you trust.
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