Mustache template validate

mustache-template-validate · version 1.0.0 · Developer tools · free, no key needed

Check Mustache template syntax (spec v1.4.2) and its partials; returns valid or the first error with line and column.

Use when you need to: validate mustache template syntax · check a mustache template for errors · find an unclosed mustache section.

Decide before calling

Read the versioned contract and the supported scope below. Reuse mustache-template-validate@1.0.0 when your input, required output and limits match it. Choose another approach for an unsupported operation.

Explain the choice

"I can use mustache-template-validate@1.0.0 for validate mustache template syntax. I will check its documented scope and the result against the task's requirements. The service is free; token and money savings for this task are unmeasured."

Supported

• validate mustache template syntax
• check a mustache template for errors
• find an unclosed mustache section
• lint mustache tags and delimiters
• mustache syntax checker with line and column
• is this mustache template well formed

Not supported

• checking whether data contains every referenced key (use mustache-variables-list)
• rendering the template (use mustache-template-render)
• validating Handlebars, Jinja or Liquid syntax
• accepting inheritance or dynamic-name extensions

Behavior

• Grammar of Mustache specification v1.4.2: tags open with the current opening delimiter ({{ by default); sigils ! # ^ / > & { and = select comment, section, inverted section, close, partial, unescaped, triple mustache and set-delimiter tags.
• Names are "." or non-empty dot-separated parts with no ASCII whitespace after trimming padding; partial names are any non-empty run without ASCII whitespace.
• A set-delimiter tag must contain exactly two whitespace-separated delimiters, neither containing "="; otherwise reason invalid_delimiter_change.
• Reasons: unclosed_tag, invalid_tag_name, invalid_delimiter_change, unexpected_section_close, mismatched_section_close (names compared exactly), unclosed_section (the outermost still-open section), unsupported_tag ({{$...}}, {{<...}}, {{>*...}}).
• The template is checked first, then each partial in code-unit order of its name with default delimiters; the first error is reported with partial (null for the template), line and column (1-based, column in code points at the opening delimiter).
• A missing partial or missing data key is not a syntax error.

Input

• template (string, required): max length 65536; Mustache template text (at most 65536 UTF-8 bytes).
• partials (object, optional): Optional map from partial name to template text; each is validated. Omitted means none.

Output

• valid (boolean, required)
• reason (one of "unclosed_tag", "invalid_tag_name", "invalid_delimiter_change", "unexpected_section_close", "mismatched_section_close", "unclosed_section", "unsupported_tag", null, required)
• partial (string or null, required)
• line (integer or null, required): min 1
• column (integer or null, required): min 1

Limits

• max template bytes: 65536
• max partials: 32
• max tags: 10000
• max section depth: 32

Example

Request input:

{
  "template": "Hello, {{name}}!"
}

Response:

{
  "result": {
    "valid": true,
    "reason": null,
    "partial": null,
    "line": null,
    "column": null
  }
}

How to call it

MCP

Connect https://computefirst.net/mcp (setup), then call execute with:

{
  "id": "mustache-template-validate",
  "version": "1.0.0",
  "input": {
    "template": "Hello, {{name}}!"
  }
}

HTTP (no key)

curl -X POST https://computefirst.net/v1/tools/mustache-template-validate/versions/1.0.0/execute \
  -H "Content-Type: application/json" \
  -d '{"template":"Hello, {{name}}!"}'

The machine-readable contract is at /v1/tools/mustache-template-validate/versions/1.0.0.

CLI

node cli.mjs run mustache-template-validate 1.0.0 --input input.json --base-url https://computefirst.net

Get the client at /clients/cli/.

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