Before a config ships or a webhook body is replayed, you want a plain answer: does this parse? This JSON validator returns a boolean, and when the document is valid it also reports the root type — object, array, strin…
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JSON Validator
JSON
Free · API · MCPToolYour platform
Use JSON Validator three ways
The free JSON Validator 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 Validator 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 Validator?
Before a config ships or a webhook body is replayed, you want a plain answer: does this parse? This JSON validator returns a boolean, and when the document is valid it also reports the root type — object, array, string, number, boolean, or null — which catches the common mistake of sending a bare array where an object was expected.
When parsing fails you get the parser's error message describing what went wrong and where, rather than a generic failure. The scope stops at syntax: there is no JSON Schema evaluation, no OpenAPI contract checking, and no field-level rules, so a document can be perfectly valid here and still be wrong for your API. Once it parses, JSON Formatter makes the structure readable.
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-validator 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 Validator?
Does it check my JSON against a schema?
No. This is syntax and parse checking only. Pair it with your own JSON Schema or OpenAPI validator for contract-level rules.
Which root types does it report?
Object, array, string, number, boolean, or null — whichever the top level of the parsed document turns out to be.
Does an invalid document return an HTTP error?
No. Invalid input is a normal result with valid: false and the parse message, so scripts can branch on the field rather than catching an exception.
What are the key features of JSON Validator?
Pass or fail with the reason
A boolean plus the parser's own message, so you know what broke rather than just that something did.
Root type reported
Catches array-versus-object mix-ups before they reach a consumer that only handles one of them.
Safe as a CI or agent gate
Invalid input returns a result object rather than throwing, which keeps smoke scripts simple.
How do you use JSON Validator?
Paste the payload
A config file, a webhook body, or generated output you do not trust yet.
Read the verdict
Valid documents report their root type; invalid ones report the parse error.
Fix or move on
Format the valid document, or correct the syntax the error message points at.
Validation versus schema checking
These are different questions and it is worth keeping them apart. Syntax validation asks whether the bytes are legal JSON — quoting, commas, brackets, escapes. Schema validation asks whether the parsed value has the fields your system requires with the types it expects.
This tool only answers the first. That still catches a large share of real incidents: a template that interpolated an unquoted value, a truncated log line, a trailing comma from a hand edit, or a file saved with smart quotes. When the answer is "valid" but your API still rejects the request, the problem has moved to the schema layer and belongs with your own contract tooling.
Where it sits in the JSON cluster
Validation is the cheapest call in the cluster, which makes it a good first step in an agent loop. If it passes, continue to JSON Formatter for a readable version, JSON to Zod for a runtime validation draft, or JSON to YAML when the destination is a config repository.
If it fails, stop. Every downstream tool in the cluster parses first anyway, so continuing just repeats the same error one call later at a higher cost.
Which core developer tools sit in this cluster?
Where do you browse more developer tools tools?
- Developer Tools tools
Browse the full Developer Tools category on ToolYour.
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Build UTM links, check ads copy limits, QA email subjects, and calculate ROAS/CPC/CTR — free in the browser; R
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