# TypeSafe > How to use TypeSafe's System One API - [Introduction](https://docs.typesafe.ai/introduction.md): Jev is TypeSafe's flagship model and the first System One model. Send state and typed questions; get structured answers your code can use directly. - [Quick start](https://docs.typesafe.ai/introduction/quickstart.md): Get up and running with Jev in 5 minutes. - [Jev with coding agents](https://docs.typesafe.ai/introduction/coding-agents.md): What Jev is (and isn't) when you're using a coding agent. - [Example use cases](https://docs.typesafe.ai/concepts/use-case-map.md): Explore TypeSafe use cases by industry and turn promising ideas into software workflows. - [System One](https://docs.typesafe.ai/concepts/system-one.md): System One models make fast, structured decisions for software. Jev is TypeSafe's flagship model and the first System One model. - [State](https://docs.typesafe.ai/concepts/state.md): What state is, how to structure it, and how to give a System One model the context it needs. - [Primitives (Questions)](https://docs.typesafe.ai/primitives.md): The TypeSafe question types, the typed answers they return, how to choose between them, and how to ask several at once. - [Choice](https://docs.typesafe.ai/primitives/choice.md): A Choice is a System One question type for selecting one option from a defined set. The answer includes the selected option, a probability for each option, and confidence. - [Score](https://docs.typesafe.ai/primitives/score.md): A Score is a System One question type for rating content against ordered, descriptive levels. The answer includes a score, a probability for each level, and confidence. - [Noul](https://docs.typesafe.ai/primitives/noul.md): A Noul question asks the TypeSafe model to evaluate a yes/no question and return the probability that the answer is yes. - [Box](https://docs.typesafe.ai/primitives/box.md): A Box is a System One question type for finding where something is in an image. The answer is the four edges of a box around it, as fractions of the image's width and height. - [Advanced: structure](https://docs.typesafe.ai/primitives/advanced.md): Instructions, Choice options, Score levels, and Noul criteria all accept JSON structure. - [Images](https://docs.typesafe.ai/images.md): Send images in a System One request: in the state, inside a question's instructions, and as the criteria a question is judged against. - [Confidence](https://docs.typesafe.ai/confidence.md): How TypeSafe reports certainty, how it differs from probability, and how to use it to control system behavior. - [How to build with TypeSafe](https://docs.typesafe.ai/concepts/how-to-build-with-system-one.md): Design AI-powered software by keeping code in control and giving System One narrow, structured decisions. - [AI primer](https://docs.typesafe.ai/introduction/machine-learning-primer.md): Why TypeSafe trains decision models with calibrated probabilities instead of optimizing for generated text. - [Patterns](https://docs.typesafe.ai/patterns.md): Architectural patterns for building systems with TypeSafe. - [Speculative fan-out](https://docs.typesafe.ai/patterns/fan-out.md): Send many questions in a single call, including speculative ones, and let your code decide what's relevant. - [Confidence-gated routing](https://docs.typesafe.ai/patterns/confidence-routing.md): Use confidence as a second axis. The answer tells you what; confidence tells you whether to act. - [Composite scoring](https://docs.typesafe.ai/patterns/composite-scoring.md): Break a complex judgment into atomic scores, combine with weights you control in code. - [Intent routing](https://docs.typesafe.ai/patterns/intent-routing.md): Classify incoming requests and route each to the optimal handler: deterministic logic, a specialist LLM, or a human. - [Cookbooks](https://docs.typesafe.ai/cookbooks.md): End-to-end recipes that show TypeSafe in real problems, from a few questions to full pipelines. - [Function calling](https://docs.typesafe.ai/cookbooks/function_calling.md): Turns natural-language trading requests into calls to ordinary typed functions by mapping function names and closed-set arguments to confidence-aware TypeSafe questions. - [Skill suggestion](https://docs.typesafe.ai/cookbooks/skill_suggestion.md): Picks at most one skill for an agent turn out of the 182 in Nous Research's Hermes catalog, using two TypeSafe requests to rank and re-check the top candidates. - [Guardrails for LLMs](https://docs.typesafe.ai/cookbooks/llm_guardrails.md): Screen every message going into and out of an LLM app with one TypeSafe request, thresholding hazard probabilities and severity to pass, review, block, or route. - [Double-checking citations](https://docs.typesafe.ai/cookbooks/citation_check.md): Catch wrong or hallucinated citations by checking against the source document. One Choice question decides whether the quote's context supports the claim. - [Classifying RAG passages](https://docs.typesafe.ai/cookbooks/classifying_rag_passages.md): Score each retrieved passage with one TypeSafe request, then decide in code which ones reach the answering model. - [Simple memory system](https://docs.typesafe.ai/cookbooks/basic_memory.md): Let Jev decide which requests and answers are worth remembering, then wrap the Jev call in a small function that adds memories to later calls. - [Hierarchical classification](https://docs.typesafe.ai/cookbooks/hierarchical_classification.md): Classifies documents through deep patent, retail product, biomedical, and source-code hierarchies using parallel beam search over TypeSafe Choice probabilities. - [Classification using confidence](https://docs.typesafe.ai/cookbooks/classification_using_confidence.md): Classify SEC annual reports into 75 industry groups with one Choice each, then read the answer's own confidence to decide whether to report that group or the broader division above it. - [Twitch chat filter](https://docs.typesafe.ai/cookbooks/twitch_chat_filter.md): Hide insults, spam, and unasked-for gameplay tips in Twitch chat, blur spoilers, and highlight questions. Each message gets one TypeSafe request containing multiple questions. Up to eight messages are processed concurrently, and the rules are defined in code. - [SDE cascade](https://docs.typesafe.ai/cookbooks/sde_cascade.md): Uses a 2-stage structured-data-extraction cascade (mini → verify → reasoning) to get most of the quality of a big reasoning model at a fraction of the cost. - [Date extraction](https://docs.typesafe.ai/cookbooks/date_extraction_cookbook.md): Extracts absolute and relative dates by asking TypeSafe for the parts named in a document, then resolving and validating them in code with confidence-based review. - [Pre-parsed value extraction](https://docs.typesafe.ai/cookbooks/pre_parsed_value_extraction_cookbook.md): Uses regexes to find candidate emails, phone numbers, and amounts, then has TypeSafe select the requested span so code can normalize a verbatim value. - [Structure recovery](https://docs.typesafe.ai/cookbooks/autoformat.md): Reconstructs Markdown from plain text that lost its formatting in two requests: one stitches hard-wrapped lines back together, one classifies every block (heading, list, code, callout). - [Re-ranking](https://docs.typesafe.ai/cookbooks/rerank_typesafe.md): Builds 30-passage BM25 shortlists for 40 CLERC legal queries, then uses one TypeSafe question per query-candidate pair to raise top-1 accuracy from 5% to 18% and top-10 accuracy from 38% to 62%. - [Line-by-line search](https://docs.typesafe.ai/cookbooks/semantic_find.md): Build semantic search for GitHub's Terms of Service. In one request, score 218 line ids against a plain-language query with a Choice question, and use a Noul question to check whether the document contains an answer. - [Knowledge graph entity alignment](https://docs.typesafe.ai/cookbooks/entity_alignment.md): Decides which of 450 candidate pairs from two beer catalogues describe the same product using one Score question plus three companion Nouls that surface which fields disagree. - [Self-consistency: choices](https://docs.typesafe.ai/cookbooks/consistency_choice_cookbook.md): Add an uncertain outcome to moderation decisions and compare label agreement with the share of automatic actions. - [Self-consistency: nouls](https://docs.typesafe.ai/cookbooks/consistency_noul_cookbook.md): Route uncertain probabilities to human review while keeping the underlying noul values visible. - [Parallel questions](https://docs.typesafe.ai/cookbooks/parallel_questions.md): Runs a 13-question regulatory briefing over the GDPR Wikipedia article, showing that batching every question into one TypeSafe call is 12.2x cheaper and 10.0x faster with no change in answers. - [Autoresearch feature discovery](https://docs.typesafe.ai/cookbooks/autoresearch_feature_discovery.md): Runs an autoresearch loop that proposes TypeSafe questions, converts free text into numeric features, and uses model errors to improve a supervised CatBoost regressor. - [Demos](https://docs.typesafe.ai/demos.md): Interactive examples showing what's possible with TypeSafe. - [Smart home assistant demo](https://docs.typesafe.ai/demos/smart-home.md): Demo code: a smart home assistant that uses TypeSafe to evaluate user requests. - [Models](https://docs.typesafe.ai/models.md) - [Agent skill](https://docs.typesafe.ai/agent-skill.md): Drop-in skill for Claude Code, Codex, and other agent environments. - [Legal](https://docs.typesafe.ai/legal.md): Legal documents and policies for TypeSafe. - [Jev 1.13 jaggedness](https://docs.typesafe.ai/model-jaggedness/jev-1.13.md): Jev isn't perfect. Here are some jagged edges we are aware of with jev-1.13. Many of these will be fixed in later versions. - [System One](https://docs.typesafe.ai/api/system-one.md): Answer one or more questions about the content supplied in `state`. - [List models](https://docs.typesafe.ai/api/list-models.md): List the models and aliases available to the authenticated account. - [Request rules and errors](https://docs.typesafe.ai/api/errors.md): Request limits, compression, and HTTP status codes - [Client SDKs](https://docs.typesafe.ai/sdk.md): Install a TypeSafe client SDK and use typed questions and answers in your application. - [TypeSafe Python SDK](https://docs.typesafe.ai/sdk/python.md): Install the TypeSafe Python SDK and get started with asynchronous or synchronous API calls. - [Basic usage](https://docs.typesafe.ai/sdk/python/usage/basic.md): Guides and patterns for working with the TypeSafe Python SDK. - [Advanced usage](https://docs.typesafe.ai/sdk/python/usage/advanced.md): Performance tuning, logging, and forward compatibility for the TypeSafe Python SDK. - [Changelog](https://docs.typesafe.ai/sdk/python/changelog.md): Python clients for the TypeSafe AI API - [API reference](https://docs.typesafe.ai/sdk/python/api.md): Python clients for the TypeSafe AI API - [Asynchronous client](https://docs.typesafe.ai/sdk/python/api/clients/async.md): Use AsyncTypeSafeClient to ask questions, list models, and configure asynchronous TypeSafe API requests. - [Synchronous client](https://docs.typesafe.ai/sdk/python/api/clients/sync.md): Use TypeSafeClient to ask questions, list models, and configure synchronous TypeSafe API requests. - [Questions](https://docs.typesafe.ai/sdk/python/api/types/questions.md): Provide state and ask yes/no, choice, and score questions using objects or dictionaries. - [Assets](https://docs.typesafe.ai/sdk/python/api/types/assets.md): Attach assets to System One requests and reference them from request content. - [Answers and responses](https://docs.typesafe.ai/sdk/python/api/types/responses.md): Read answers, confidence scores, token usage, and available models returned by the TypeSafe API. - [Retries](https://docs.typesafe.ai/sdk/python/api/retries.md): Configure retries with RetryPolicy — attempt count, retryable statuses, backoff, and retry headers handling. - [Common types](https://docs.typesafe.ai/sdk/python/api/types/common.md): Common types for TypeSafe API SDK. - [Exceptions](https://docs.typesafe.ai/sdk/python/api/exceptions.md): Handle TypeSafe API errors, rate limits, connection failures, and timeouts. - [Constants](https://docs.typesafe.ai/sdk/python/api/constants.md): Default settings and environment variable names for the TypeSafe Python SDK. - [JavaScript SDK](https://docs.typesafe.ai/sdk/javascript.md) - [Changelog](https://docs.typesafe.ai/sdk/javascript/changelog.md) - [API reference](https://docs.typesafe.ai/sdk/javascript/api.md) - [Class: APIConnectionError](https://docs.typesafe.ai/sdk/javascript/api/classes/APIConnectionError.md) - [Class: APIError](https://docs.typesafe.ai/sdk/javascript/api/classes/APIError.md) - [Class: APIPromise](https://docs.typesafe.ai/sdk/javascript/api/classes/APIPromise.md) - [Class: APITimeoutError](https://docs.typesafe.ai/sdk/javascript/api/classes/APITimeoutError.md) - [Class: APIUserAbortError](https://docs.typesafe.ai/sdk/javascript/api/classes/APIUserAbortError.md) - [Class: AuthenticationError](https://docs.typesafe.ai/sdk/javascript/api/classes/AuthenticationError.md) - [Class: BadRequestError](https://docs.typesafe.ai/sdk/javascript/api/classes/BadRequestError.md) - [Class: Image](https://docs.typesafe.ai/sdk/javascript/api/classes/Image.md) - [Class: InternalServerError](https://docs.typesafe.ai/sdk/javascript/api/classes/InternalServerError.md) - [Class: NotFoundError](https://docs.typesafe.ai/sdk/javascript/api/classes/NotFoundError.md) - [Class: PermissionDeniedError](https://docs.typesafe.ai/sdk/javascript/api/classes/PermissionDeniedError.md) - [Class: RateLimitError](https://docs.typesafe.ai/sdk/javascript/api/classes/RateLimitError.md) - [Class: TypeSafeClient](https://docs.typesafe.ai/sdk/javascript/api/classes/TypeSafeClient.md) - [Class: TypeSafeError](https://docs.typesafe.ai/sdk/javascript/api/classes/TypeSafeError.md) - [Class: UnprocessableEntityError](https://docs.typesafe.ai/sdk/javascript/api/classes/UnprocessableEntityError.md) - [Interface: BoxCoordinates](https://docs.typesafe.ai/sdk/javascript/api/interfaces/BoxCoordinates.md) - [Interface: BoxQuestion](https://docs.typesafe.ai/sdk/javascript/api/interfaces/BoxQuestion.md) - [Interface: BoxResponse](https://docs.typesafe.ai/sdk/javascript/api/interfaces/BoxResponse.md) - [Interface: ChoiceQuestion](https://docs.typesafe.ai/sdk/javascript/api/interfaces/ChoiceQuestion.md) - [Interface: ChoiceResponse](https://docs.typesafe.ai/sdk/javascript/api/interfaces/ChoiceResponse.md) - [Interface: Logger](https://docs.typesafe.ai/sdk/javascript/api/interfaces/Logger.md) - [Interface: ModelCard](https://docs.typesafe.ai/sdk/javascript/api/interfaces/ModelCard.md) - [Interface: Models](https://docs.typesafe.ai/sdk/javascript/api/interfaces/Models.md) - [Interface: NoulQuestion](https://docs.typesafe.ai/sdk/javascript/api/interfaces/NoulQuestion.md) - [Interface: NoulResponse](https://docs.typesafe.ai/sdk/javascript/api/interfaces/NoulResponse.md) - [Interface: Questions](https://docs.typesafe.ai/sdk/javascript/api/interfaces/Questions.md) - [Interface: RequestOptions](https://docs.typesafe.ai/sdk/javascript/api/interfaces/RequestOptions.md) - [Interface: RetryPolicy](https://docs.typesafe.ai/sdk/javascript/api/interfaces/RetryPolicy.md) - [Interface: ScoreQuestion](https://docs.typesafe.ai/sdk/javascript/api/interfaces/ScoreQuestion.md) - [Interface: ScoreResponse](https://docs.typesafe.ai/sdk/javascript/api/interfaces/ScoreResponse.md) - [Interface: SystemOneRequest](https://docs.typesafe.ai/sdk/javascript/api/interfaces/SystemOneRequest.md) - [Interface: SystemOneResult](https://docs.typesafe.ai/sdk/javascript/api/interfaces/SystemOneResult.md) - [Interface: TextWithAssets](https://docs.typesafe.ai/sdk/javascript/api/interfaces/TextWithAssets.md) - [Interface: TypeSafeClientConfig](https://docs.typesafe.ai/sdk/javascript/api/interfaces/TypeSafeClientConfig.md) - [Interface: Usage](https://docs.typesafe.ai/sdk/javascript/api/interfaces/Usage.md) - [Interface: WithResponse](https://docs.typesafe.ai/sdk/javascript/api/interfaces/WithResponse.md) - [Type Alias: Asset](https://docs.typesafe.ai/sdk/javascript/api/type-aliases/Asset.md) - [Type Alias: ChoiceCriteria](https://docs.typesafe.ai/sdk/javascript/api/type-aliases/ChoiceCriteria.md) - [Type Alias: Compression](https://docs.typesafe.ai/sdk/javascript/api/type-aliases/Compression.md) - [Type Alias: ContentValue](https://docs.typesafe.ai/sdk/javascript/api/type-aliases/ContentValue.md) - [Type Alias: Description](https://docs.typesafe.ai/sdk/javascript/api/type-aliases/Description.md) - [Type Alias: EntryType](https://docs.typesafe.ai/sdk/javascript/api/type-aliases/EntryType.md) - [Type Alias: EnvVar](https://docs.typesafe.ai/sdk/javascript/api/type-aliases/EnvVar.md) - [Type Alias: Fetch](https://docs.typesafe.ai/sdk/javascript/api/type-aliases/Fetch.md) - [Type Alias: JsonValue](https://docs.typesafe.ai/sdk/javascript/api/type-aliases/JsonValue.md) - [Type Alias: LogLevel](https://docs.typesafe.ai/sdk/javascript/api/type-aliases/LogLevel.md) - [Type Alias: Question](https://docs.typesafe.ai/sdk/javascript/api/type-aliases/Question.md) - [Type Alias: ResultFor](https://docs.typesafe.ai/sdk/javascript/api/type-aliases/ResultFor.md) - [Type Alias: ScoreCriteria](https://docs.typesafe.ai/sdk/javascript/api/type-aliases/ScoreCriteria.md) - [Type Alias: ScoreLegend](https://docs.typesafe.ai/sdk/javascript/api/type-aliases/ScoreLegend.md) - [Type Alias: ScoreOf](https://docs.typesafe.ai/sdk/javascript/api/type-aliases/ScoreOf.md) - [Type Alias: SentContent](https://docs.typesafe.ai/sdk/javascript/api/type-aliases/SentContent.md) - [Variable: ENV](https://docs.typesafe.ai/sdk/javascript/api/variables/ENV.md) - [Variable: LOG_LEVELS](https://docs.typesafe.ai/sdk/javascript/api/variables/LOG_LEVELS.md) - [Variable: noul](https://docs.typesafe.ai/sdk/javascript/api/variables/noul.md) - [Variable: score](https://docs.typesafe.ai/sdk/javascript/api/variables/score.md) - [Variable: VERSION](https://docs.typesafe.ai/sdk/javascript/api/variables/VERSION.md) - [Variable: withAssets](https://docs.typesafe.ai/sdk/javascript/api/variables/withAssets.md) - [Function: box()](https://docs.typesafe.ai/sdk/javascript/api/functions/box.md) - [Function: choice()](https://docs.typesafe.ai/sdk/javascript/api/functions/choice.md) - [Function: image()](https://docs.typesafe.ai/sdk/javascript/api/functions/image.md) ## OpenAPI Specs - [openapi](https://api.typesafe.ai/openapi.json) This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.