API Contract Designer
Expert API architect for designing consistent REST/GraphQL contracts, resource models, and OpenAPI specs.
- Model complex resource relationships and lifecycles before implementation
- Generate consistent OpenAPI skeletons with standardized error envelopes
- Audit existing API designs for idempotency and retry safety
$9.99
· or 50 creditsSecure checkout via Stripe
Included in download
- Model complex resource relationships and lifecycles before implementation
- Generate consistent OpenAPI skeletons with standardized error envelopes
- Ready for Compatible with Claude Code
Sample input
Design a REST API for a subscription-based coffee delivery service including resource modeling and a standard error envelope. Use snake_case.
Sample output
Resources: /customers, /subscriptions, /roasts. Relationships: Customer has-many Subscriptions. Error Envelope: { "error": { "code": "string", "message": "string", "details": [], "request_id": "uuid" } } Idempotency: PUT /subscriptions/{id}/pause requires X-Idempotency-Key.
Expert API architect for designing consistent REST/GraphQL contracts, resource models, and OpenAPI specs.
$9.99
· or 50 creditsSecure checkout via Stripe
Included in download
- Model complex resource relationships and lifecycles before implementation
- Generate consistent OpenAPI skeletons with standardized error envelopes
- Ready for Compatible with Claude Code
- Instant install
Sample input
Design a REST API for a subscription-based coffee delivery service including resource modeling and a standard error envelope. Use snake_case.
Sample output
Resources: /customers, /subscriptions, /roasts. Relationships: Customer has-many Subscriptions. Error Envelope: { "error": { "code": "string", "message": "string", "details": [], "request_id": "uuid" } } Idempotency: PUT /subscriptions/{id}/pause requires X-Idempotency-Key.
About This Skill
What it does
The API Contract Designer is a specialized architect for your AI agent that ensures your APIs are consistent, scalable, and developer-friendly before a single line of code is written. It shifts focus from "endpoints" to "resource modeling," helping you define the nouns, relationships, and lifecycles of your domain. It handles the heavy lifting of cross-cutting concerns like idempotency, error envelopes, and pagination strategies.
Why use this skill
Generic AI prompts often produce brittle, inconsistent APIs that lack cohesive naming or proper error handling. This skill enforces "consistency by construction" by forcing high-level design decisions—such as auth patterns and versioning strategies—across the entire contract. It proactively flags non-idempotent operations and designs retry logic to prevent distributed systems failures.
Supported Standards & Outputs
- REST and GraphQL architectural styles
- OpenAPI Spec (OAS) skeleton generation
- Resource lifecycle modeling and relationship mapping
- Webhook and event-driven architecture design
- Standardized error envelopes and pagination (Cursor/Offset)
The output is a production-ready blueprint, ranging from structured audit reports to copy-paste OpenAPI templates tailored to your specific tech stack and team constraints.
Use Cases
- Model complex resource relationships and lifecycles before implementation
- Generate consistent OpenAPI skeletons with standardized error envelopes
- Audit existing API designs for idempotency and retry safety
- Standardize naming conventions and pagination across multiple services
- Design robust webhook and event-driven notification schemas
Known Limitations
- Requires manual input for business logic details.
- Does not generate implementation code.
- Best for greenfield design rather than legacy refactors.
How to Install
mkdir -p ~/.claude/skills && curl -sL https://www.agensi.io/api/install/api-contract-designer -o /tmp/api-contract-designer.zip && unzip -o /tmp/api-contract-designer.zip -d ~/.claude/skills && rm /tmp/api-contract-designer.zipFree skills install directly. Paid skills require purchase - use the download button above after buying.
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Security Scanned
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Permissions
No special permissions declared or detected
Compatible with Claude Code, Cursor, and Cline.
Frequently Asked Questions
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