You have a real response from an endpoint that has no published types, and hand-writing the interface is twenty minutes of tedious transcription.
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JSON to TypeScript
Type / schema name
JSON
Free · API · MCPToolYour platform
Use JSON to TypeScript three ways
The free JSON to TypeScript on this page works in your browser. The same workflow is available via REST API for apps and via MCP for Cursor, Claude, and other agents — one API key, one plan, one quota. This tool is part of the developer-apis module under Developer Tools.
- Free in browserUse JSON to TypeScript here — no account required.
- REST APICall from your server with
X-Api-Key. - MCP for agentsConnect Cursor or Claude to ToolYour MCP with the same key.
- 1. Get an API keySign in and open Dashboard → API Keys (works for REST and MCP).
- 2. Call or connectUse the REST API from your server, or paste the MCP URL into your agent config.
- 3. Same qualityOutput matches the free web tool across all three surfaces.
What is JSON to TypeScript?
You have a real response from an endpoint that has no published types, and hand-writing the interface is twenty minutes of tedious transcription. This JSON to TypeScript converter walks the sample and emits a single exported type with nested object shapes inlined, so you get a compiling starting point in one step.
Be clear about what inference from one sample can and cannot know. Arrays are typed from their first element, so a mixed array narrows incorrectly. Empty arrays become unknown arrays because there is nothing to infer from. Every present field looks required, and every absent field does not exist at all — optionality and unions are invisible to a single example. Empty objects widen to a record of unknown. Treat the output as a scaffold, then refine it in your editor. When you want runtime checking rather than compile-time types, JSON to Zod generates a schema from the same sample.
Browser use is free and needs no signup. The same job runs over REST at POST https://api.toolyour.com/api/v1/developer-apis/json-to-typescript and over MCP at https://api.toolyour.com/mcp — one API key, one shared monthly credit pool, 1 credit per successful call.
What are common questions about JSON to TypeScript?
Is this JSON Schema to TypeScript?
No. It infers from one example document rather than reading a schema, so it cannot know about optional fields, unions, or format constraints.
Can I choose the type name?
Yes. Pass a name and it is sanitised into a valid identifier; the default root type is called Root.
Why did my array become unknown[]?
Because it was empty in the sample. Supply an example containing at least one representative element and the element type is inferred.
Are optional fields detected?
No. A single sample cannot distinguish optional from always-present, so add the question marks yourself where the API allows the field to be absent.
What are the key features of JSON to TypeScript?
Nested shapes inlined
Objects and arrays are walked recursively into one readable exported type.
Named root type
Supply your own type name, sanitised into a valid TypeScript identifier.
Predictable widening
Empty arrays and empty objects widen to unknown rather than guessing a shape that is not in the sample.
How do you use JSON to TypeScript?
Paste a representative response
Pick the fullest example you have — richer samples infer better types.
Name the type
Give the root a meaningful name so it reads well at the call site.
Refine in your editor
Add optionality, unions, and literal types the sample could not reveal.
What one sample can never tell you
Inference is bounded by evidence, and a single document carries four blind spots worth checking by hand every time.
**Optionality** — a field present in your sample may be omitted in others; the generated type will claim it is always there. **Unions** — a field that is sometimes a string and sometimes null appears as whichever you happened to capture. **Enumerations** — a status field becomes
string rather than a literal union of the values your API actually returns. **Numeric intent** — an identifier that arrives as a number is typed as number even when it is really an opaque key that should never be arithmetic.
Two minutes of editing after generation removes most of the risk, and the resulting type is far better than one transcribed by hand.Choosing a target in the codegen cluster
The same sample feeds four generators, and the right one depends on where the checking happens. Use this tool for compile-time types in TypeScript. Use JSON to Zod when you need runtime validation at a trust boundary and a type inferred from the schema. Use JSON to Go Struct for a Go client, and JSON to Python for a Python dataclass sketch.
Whichever you pick, validate the sample first with JSON Validator — every generator parses before it emits, and a parse error at that stage is cheaper to read.
Which JSON / data codegen tools sit in this cluster?
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