server.json Validator. Check it before you publish.
Paste your MCP Registry server.json and check it against the official 2025-12-11 schema and the registry's own publishing rules, without leaving your browser.
Validate your server.json
Your file stays in this page. Nothing is uploaded.
Checked against the official server.json schema 2025-12-11 and the registry’s official registry requirements, as of 28 October 2026. Your file stays in this page.
Schema: server.schema.json 2025-12-11. Publishing rules: the registry's documentation. Both checked 28 October 2026.
How to use it
How to use the server.json Validator
Paste the whole file, or load the valid or broken example to see how it works, then select Validate. Errors block publishing; warnings are accepted but worth fixing.
Each message names the field, such as packages[0].version, and what is wrong. Below the results is the list of checks the registry runs only when you publish, such as proving you own the namespace.
Limits
What it can't tell you
It can't run the checks that need the internet or your accounts: namespace ownership, whether your npm or PyPI package exists and names the server, OCI image labels, or whether a version was already published. The registry runs those when you publish.
The registry and its schema still change. We implemented schema 2025-12-11, the current version on 28 October 2026. Files on older schema versions get a warning, as the registry gives.
FAQ
Common questions
What is server.json?
Which fields are required in server.json?
Why is my description rejected?
Can I use a version range like ^1.0.0?
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