JSON Schema
JSON Schema is a declarative specification language for describing and validating the structure of JSON data, itself written in JSON format. It defines rules covering data types, property constraints, required fields, and enumerated values to validate and document JSON data. JSON Schema is widely used in API design, configuration file validation, form validation, and automated code generation, serving as a key tool for ensuring interoperability and data consistency.
Core Facts
Each tool in MCP has a strict JSON Schema description, including the name, functional description, and parameter specifications
Function Calling机制中，开发者将工具的名称、功能描述、参数Schema（通常为JSON Schema格式）注入到模型的请求中，模型输出结构化的JSON而非自然语言来调用工具
JSON Schema is a specification for describing and validating JSON data structures, capable of defining field requirements, data types, and value ranges.
Timeline (last 90 days)
Deterministic checks (such as regex matching, JSON Schema validation, keyword blacklists) have execution overhead at the microsecond to millisecond level and always give the same result for the same input, and should be executed inline on every request.
In AI document review, type safety can constrain large model output structure through schema definition tools such as JSON Schema, Pydantic and Zod, for example forcing contract amounts to be of numeric type and effective dates to conform to the ISO 8601 format.
In MCP, JSON schema is used to describe tool input parameters; the host can use it to automatically generate call forms, validate parameters or reject invalid parameters in advance, but it does not constrain whether a tool should be called or whether a call is authorized.
Schema compliance from any provider only guarantees shape, not semantic correctness; for example, a sign error on an offset row can pass strict JSON-schema validation.
APIMock-AI's ContractTester sends requests to real or Mock services, then uses JSON Schema to verify whether the request body and response body conform to the contract.
In the OpenAI Function Calling specification, a tool of medium complexity (such as one with 5-8 parameters, including nested objects) typically consumes 150-400 Tokens for its JSON Schema.
Engineering practices for addressing LLM uncertainty include using structured outputs (such as JSON Schema constraints), setting confidence thresholds below which cases are routed to humans, and building independent validation layers.
When model output does not conform to the expected schema, the workflow should route that record to a manual review queue rather than silently falling back to default values.
Ollama supports structured output mode when running open-source models locally, enforcing token sampling to conform to a specified Schema at the underlying level through grammar-constrained decoding.
By defining a JSON Schema in the system prompt, Gemini can be required to return extraction results strictly in a predefined field format, allowing downstream nodes to read field values directly without additional parsing.
40 more timeline events
All Facts (20)
Each tool in MCP has a strict JSON Schema description, including the name, functional description, and parameter specifications
90%VerifiedFunction Calling机制中，开发者将工具的名称、功能描述、参数Schema（通常为JSON Schema格式）注入到模型的请求中，模型输出结构化的JSON而非自然语言来调用工具
80%VerifiedJSON Schema is a specification for describing and validating JSON data structures, capable of defining field requirements, data types, and value ranges.
80%VerifiedStructured output imposes constraints on token generation during the decoding phase through JSON Schema or function-calling mechanisms, which is fundamentally different from requesting JSON-format output in the prompt.
80%VerifiedDefining typed JSON Schema for tools can reduce format errors and hallucinated parameter filling during model calls, improving call success rates.
75%VerifiedJSON Schema is a declarative specification based on JSON format, originating from a community draft in 2009, with standardization work advanced by the IETF in RFC 8927 and subsequent drafts.
75%VerifiedSetting additionalProperties: false in a JSON Schema rejects any extra fields not explicitly declared in the schema, eliminating the possibility of the model inventing additional fields.
75%VerifiedThe latest version of JSON Schema is Draft 2020-12, maintained by json-schema.org.
75%VerifiedJSON Schema is maintained by the IETF, and the current version is Draft 2020-12.
70%VerifiedSwagger已更名为OpenAPI Specification，是一套用于描述RESTful API的标准化规范，以JSON或YAML格式定义API信息，目前业界广泛使用OpenAPI 3.0/3.1版本
70%VerifiedIn the tool-calling mechanism, developers attach a tool description list in JSON Schema format when calling the LLM API, and the model outputs call parameters in structured JSON format
65%VerifiedThe schema for tool calls is essentially a JSON Schema specification that describes the tool name, parameter names, type constraints, and required fields.
65%VerifiedMCP规定了工具描述的标准格式，包括工具名称、参数schema、返回值格式
65%VerifiedTaking GPT-4o as an example, the JSON Schema description of each tool consumes an average of 200–500 tokens, and when the system integrates 50 tools, the tool description section alone consumes 10,000 to 25,000 tokens.
65%UnverifiedHermes模型从微调阶段就大量使用结构化输出训练数据，使模型天然倾向于生成格式正确的JSON
80%Unverified当前版本的ChatGPT支持通过JSON Schema或函数调用（Function Calling）约束模型输出特定格式的数据结构
80%UnverifiedFunction Call通过JSON Schema定义工具，能让大模型以接近100%的准确率生成合法的工具调用请求
70%UnverifiedOutlines implements a compilation pipeline from Pydantic models to JSON Schema to FSM, enabling developers to obtain generation constraints simply by defining Pydantic classes.
60%UnverifiedDeterministic checks (such as regex matching, JSON Schema validation, keyword blacklists) have execution overhead at the microsecond to millisecond level and always give the same result for the same input, and should be executed inline on every request.
50%UnverifiedIn AI document review, type safety can constrain large model output structure through schema definition tools such as JSON Schema, Pydantic and Zod, for example forcing contract amounts to be of numeric type and effective dates to conform to the ISO 8601 format.
50%