Prompt Variable Validator
Find missing, unused, and repeated template variables across prompt text and a sample JSON payload.
Also useful for: prompt template validator prompt variable checker template variable validator prompt placeholder checker Prompt Variable Validator
Prompt Variable Validator
Runs in your browser. Inputs are not uploaded.Prompt Variable Validator Example Run
Compare template variables with a sample payload.
Sample inputs
Template
Prompt template:
Write a {{tone}} email to {{customer_name}} about ${product}.
Payload
Sample JSON payload:
{"tone":"friendly","customer_name":"Ada","unused":"not referenced"}
Generated result
Summary: 3 unique prompt variables found. 1 error, 1 warning.
Stats
- Variables: 3
- Payload Keys: 3
Issues
- Critical: product is used in the template but missing from the sample payload.
- Warning: unused exists in payload but is not used in the template.
Output
Variables:
- tone
- customer_name
- product
[ERROR] general: product is used in the template but missing from the sample payload.
[WARNING] general: unused exists in payload but is not used in the template. What the Prompt Variable Validator Checks
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Template variable inventory
Variables in double braces and similar placeholder shapes are collected into a readable list.
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Missing payload keys
Template variables are compared with the sample JSON payload so runtime gaps are visible.
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Unused payload keys
Payload keys that never appear in the template are reported as cleanup candidates.
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Repeated variables
Repeated placeholders are counted so intentional reuse is visible rather than surprising.
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Flat JSON focus
The payload check is designed for flat sample objects, not full template-engine execution.
Prompt Variable Validator Questions
- Q: Does the prompt variable validator upload my prompt template? A: No. Inputs are processed in your browser, and pasted content is not sent to analytics or a server.
- Q: What should I paste into the prompt variable validator? A: Paste the template, then a separator line with three hyphens, then a sample JSON payload.
- Q: What can I copy or download? A: You can copy the variable inventory and missing/unused key report.
- Q: What does the prompt variable validator not verify? A: It does not render Jinja, Handlebars, or nested conditionals; it checks placeholder names and a sample payload.
Related Tools
Updates
- v1.0.0 New 2026-05-17: Initial placeholder inventory, missing-key, and unused-key checks added.