Spec0
Give Cursor and Claude Code live access to your private OpenAPI specs via MCP.
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Description
Give Cursor and Claude Code live access to your private OpenAPI specs via MCP. Push once, every agent queries your catalog, always current, 300 tokens instead of 150k.
About Spec0
What is Spec0?
Spec0 is a managed internal API registry with an MCP layer for AI agents. It indexes published OpenAPI specifications into operations, components and metadata.
What Spec0 does
Teams push specifications through CI, a CLI or the web interface, and agents query relevant contract content through the registry. Spectral linting, breaking-change detection, team ownership and query audit logs support governance. Published specifications can also generate schema-based mock endpoints with expression rules for response behavior.
Who Spec0 is for
The site identifies Cursor and Claude Code workflows and an early-access design-partner program for engineering organizations.
How Spec0 works
The team creates an account with a private organization registry and MCP endpoint. A CLI authenticates and pushes a spec, which is indexed and checked. MCP client configuration connects the agent to organization-scoped content. Mock URLs and contract tests can then support frontend work and CI checks against the published specification.
Key features
- OpenAPI specs are indexed by operation and component.
- CI, CLI and web pushes feed one registry.
- Spectral linting checks published specs.
- Breaking changes are detected.
- Team ownership routes alerts.
- MCP queries have an audit log.
- Mock responses follow schema content.
- Expression rules customize mock behavior.
Facts from spec0.io, checked 13 October 2026
- The managed registry is hosted in the EU.
Written from Spec0's own website (Homepage, Features). The maker can claim this listing to edit it.
Categories
Frequently asked questions
Which parts can be self-hosted?
The mock server is MIT and the CLI is Apache-2.0, with self-hosting supported. The registry and MCP layer are managed services.
Does the service run the agent’s model?
No. The FAQ says the agent uses its own OpenAI or Anthropic account while Spec0 serves spec content.
Can a specification be deleted?
The FAQ says specs can be deleted through the CLI or API.
Which clients are named?
The site names Cursor, Claude Code, Claude Desktop, Continue.dev and Cline, plus other MCP clients.
Can mock behavior be changed?
Expression rules can return different statuses or payloads based on request conditions such as identifiers or query parameters.