# 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](/v1/tools/mustache-template-validate/versions/1.0.0) 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:

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

Response:

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

## How to call it

### MCP

Connect `https://computefirst.net/mcp` ([setup](/docs#connect)), then call `execute` with:

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

### HTTP (no key)

```sh
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](/v1/tools/mustache-template-validate/versions/1.0.0).

### CLI

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

Get the client at [/clients/cli/](/clients/cli/).

## Related tools

- [Mustache template render](/tools/mustache-template-render): Render a logic-less Mustache template (spec v1.4.2) with JSON data and inline partials; returns the exact text.
- [Mustache variables list](/tools/mustache-variables-list): List the names and partials a Mustache template references, with tag kind, line, column and enclosing sections.
- [Shell argv quote](/tools/shell-argv-quote): Quote inert argv strings for POSIX sh or PowerShell 7, returning a command and its per-argument fragments.
- [Git renames detect](/tools/git-renames-detect): Detect deterministic one-to-one Git-style rename pairs, unmatched paths, scores, and byte evidence.
- [Openapi operation extract](/tools/openapi-operation-extract): Extract one OpenAPI operation, merge inherited parameters, and return its local component-reference closure.
- [Commit conventional parse](/tools/commit-conventional-parse): Parse one Conventional Commits 1.0.0 message into its header, body, footers, and breaking-change status.