API Contract Tester
API Contract Tester: A focused contract checker for finding API schema violations before they reach production. Ranked #10 of 22 in Contract Testing Tools by our editors (8.3/10); pricing: Free plan; best for developers checking API schema mismatches quickly.
At a glance
- Editor score8.3 / 10
- PricingFree plan
- Best forDevelopers checking API schema mismatches quickly
- Free planYes
- Paid from$19/mo
- Facts checked20 Sep 2026
Where it wins
- Compares TypeScript or OpenAPI expectations with actual API responses
- Finds missing, extra, type, null, nested, array, and enum violations
- Runs locally through npx and supports Cline and Claude Code
Where it doesn't
- The documented MCP integrations center on Cline and Claude Code
- Free access is limited to 100 executions per month
- Advanced team and self-hosting features require the Enterprise tier
Our verdict on API Contract Tester
API Contract Tester is a local MCP server and browser-based tool for comparing expected API schemas with actual responses. It is aimed at developers who need to identify frontend-backend contract mismatches quickly, whether expectations are defined in TypeScript or OpenAPI. The tool checks missing and extra fields, type mismatches, null violations, nested objects, arrays, enums, and optional fields. Developers can also use its online contract-comparison demo or incorporate contract checks into CI/CD workflows.
Pricing is presented through ClineTools plans. The Free plan costs $0 per month with annual billing and includes all 42+ MCP tools, 100 executions per month, the full tool catalog, installation tutorials, and a community forum. Individual Dev costs $19 per month and adds 5,000 executions, priority support, early access to new tools, premium deep-dive tutorials, and a private community channel. Pro AI Agent costs $49 per month with 50,000 executions, advanced premium modules, a faster processing queue, team analytics for five members, and monthly live Q&A sessions. Enterprise costs $499 per month and adds unlimited executions, self-hosted deployment, private LLM integration, team management, SLA, and dedicated support.
Its strongest fit is teams that want structured response validation without limiting checks to simple top-level fields. Mismatch reports with fix suggestions make the output more actionable, while local operation through npx supports a self-hosted workflow. Cline and Claude Code users have documented MCP configuration paths, and the browser demo offers a separate way to compare contracts. Choose API Contract Tester for focused schema comparison and violation detection; consider an alternative if your workflow depends on a broader integration ecosystem or does not use its supported MCP setup.
Questions about API Contract Tester
Does API Contract Tester have a free plan? Yes, there is a free plan; paid plans start at $19/mo (Individual Dev).
How much does API Contract Tester cost? API Contract Tester lists 3 paid plans; the lowest is Individual Dev at $19/mo.
What does API Contract Tester run on? Web. It runs in the cloud and self-hosted.
What does API Contract Tester integrate with? 2 integrations: Cline and Claude Code.
Who is API Contract Tester built for? Solo users, small businesses and mid-market companies (our editorial estimate).
Your product? Our editors can test API Contract Tester in depth and publish a review, labelled as paid · from $149/mo →
API Contract Tester pricing
All 4 API Contract Tester plans and prices →
API Contract Tester fact sheet
| Free plan | Yes |
|---|---|
| Paid from | $19/mo |
| Contract formats | TypeScript, OpenAPI, JSON |
| Consumer verification | Not verified |
| Provider verification | Not verified |
| Contract registry | Not verified |
| AsyncAPI support | Not verified |
| GraphQL support | Not verified |
| Self-hosted deployment | Yes |
| Deployment | Cloud, Self-hosted |
| Platforms | Web |
| Support | Community, Docs |
| Built for | Solo, Small business, Mid-market (editorial estimate) |
| Integrations | 2 integrations: Cline, Claude Code |
| Pricing | Free plan (source) |
| Website | clinetools.com |
| Facts checked | 20 Sep 2026 |
API Contract Tester integrations
API Contract Tester lists 2 integrations on its own site.
- Cline
- Claude Code
Alternatives to API Contract Tester
- PactA broad open-source toolkit for consumer-driven contracts across HTTP and message integrations.9.4
- MicrocksA broad contract-testing choice for APIs, microservices, and event-driven systems.9.2
- PactFlowPactFlow brings Pact, OpenAPI testing, contract management, and deployment checks together.9.0
See all API Contract Tester alternatives →
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Reviewed by iTechGuides Editors · Editorial team · Updated Nov 2026
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