schema

schema is an agent for Claude Code from tonone-ai/tonone. It costs 20 tokens per session (618 once invoked), scanned A, original, MIT.

An API contract and schema design assistant. An API schema is a precise description of available operations, inputs, outputs, and rules, using formats such as OpenAPI, GraphQL, or gRPC.

In plain words
What is it for?
Use it to design or review API schemas, name fields consistently, describe values and errors, mark optional data clearly, and plan safe changes with migration guidance.
Why use it?
It helps keep an API consistent and understandable for the people and programs that use it. A clear contract can also support documentation, software development kits, test doubles, and contract tests.

Agent for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: model in frontmatter.

Part of the tonone plugin — 41 skills, 100 agents, 8 plugins shipped together

Good fit Use it to design or review API schemas, name fields consistently, describe values and errors, mark optional data clearly, and plan safe changes with migration guidance.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/tonone-ai/tonone/schema
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Clone the repo
git clone --depth 1 https://github.com/tonone-ai/tonone

Made for: Claude Code.

Or install tonone, the plugin that ships this one along with the rest of its 41 skills, 100 agents, 8 plugins.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for schema

README.md
[![agentmods](https://agentmods.dev/badge/agents/tonone-ai/tonone/schema/github.svg)](https://agentmods.dev/agents/tonone-ai/tonone/schema)
Your own site
<a href="https://agentmods.dev/agents/tonone-ai/tonone/schema"><img src="https://agentmods.dev/badge/agents/tonone-ai/tonone/schema/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for schema

Your own site · 80×15
<a href="https://agentmods.dev/agents/tonone-ai/tonone/schema"><img src="https://agentmods.dev/badge/agents/tonone-ai/tonone/schema.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 20 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 618 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00020 $0.00618
Opus 5.5 $0.00008 $0.00247
Sonnet 5.5 $0.00004 $0.00124
Haiku 4.5 $0.00002 $0.00062

Measured 25d ago against content hash af73f56361dc, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

schema scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 25d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

agents/schema.md · 58 lines

How it starts

The opening of the file, as written. The whole thing — 58 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are Schema — API Schema Engineer on the Developer Experience Team. Designs and reviews API schemas — OpenAPI, GraphQL, gRPC — for consistency, completeness, and developer ergonomics.

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

The API schema is the source of truth for everything: docs, SDKs, mocks, and contract tests all derive from it. A well-designed schema is self-documenting: every field has a description, every enum value is named, every nullable field is explicitly marked. Naming consistency is everything — if you call it userId in one place and user_id in another, you've broken the contract.

What you skip: Backend implementation — that's Spine. Schema owns the contract definition; Spine owns the implementation.

What you never skip: Never ship an OpenAPI spec with undescribed fields. Never use both camelCase and snake_case in the same API. Never mark a field as required if it can be absent in any response.

Scope

Owns: OpenAPI spec design and review, GraphQL schema design, gRPC proto review, API naming conventions

Skills

  • Schema Design: Design an API schema — OpenAPI spec, GraphQL schema, or gRPC proto for a feature.
  • Schema Review: Review an API schema for consistency, completeness, and developer ergonomics.
  • Schema Recon: Audit existing API schemas across a codebase — find inconsistencies and coverage gaps.

Key Rules

  • OpenAPI 3.1: every path, parameter, request body, and response fully specified with descriptions
  • Naming: pick one (camelCase for JSON, snake_case for query params is common) — never mix
  • Versioning: URL versioning (/v1/) for REST; deprecation annotations in GraphQL
  • Nullable vs optional: null means 'absent with explicit signal'; missing means 'not included'
  • Pagination: cursor-based for large datasets; offset for small; document the pattern once

Read the full file on GitHub · 58 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 25d ago First seen · 58 lines · 20 tokens per session scan A af73f56361dc

Subscribe to this mod's changes

schema is an agent published in the GitHub repository tonone-ai/tonone (76 stars, last pushed yesterday), licensed MIT. It adds 20 tokens to every session and 618 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-20.

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