---
title: "vastlint"
description: "Validate VAST, VMAP, and DAAST ad tags against IAB Tech Lab specs. Hosted MCP at https://vastlint.org/mcp. Auth none for public tools."
canonical: https://agentpluginsdirectory.com/plugins/vastlint
last-updated: 2026-10-21
---

# vastlint
Validate VAST, VMAP, and DAAST ad tags against IAB Tech Lab specs. Hosted MCP at https://vastlint.org/mcp. Auth none for public tools.
- Slug: vastlint
- Publisher: aleksUIX
- Repository: https://github.com/aleksUIX/vastlint
- Manifest: plugin.json
- Version: 0.13.9
- License: Apache-2.0
- Category (editorial): code-review
- Skills: 2 (inspect-vast, validate-vast)
- MCP servers: 1 (vastlint)
- Stars: 19
- Repository created: 2026-04-03
- Repository last pushed: 2026-10-21
- Publisher type: User
- Listing: https://agentpluginsdirectory.com/plugins/vastlint
- Schema: https://agent-plugins.org/schemas/1.0.0/plugin.schema.json

## What vastlint does, in the publisher's words

Website & web validator: VAST tag validator Paste a VAST tag and get results in your browser, no install required.

A high-performance VAST XML validator built on a pure-Rust core. Checks ad tags against the IAB Tech Lab VAST specification so you don't have to read it. Over $30 billion in annual CTV and video ad spend flows through VAST XML, and malformed tags are one of the most common causes of lost impressions, broken tracking, and revenue discrepancies between platforms. There is no widely adopted open-source tool that validates VAST XML against the full IAB specification across all published versions.

VASTlint ships a native MCP server: making VAST validation available as a callable tool from Claude, Cursor, the AAMP Buyer Agent SDK, or any MCP-compatible client. Connect to vastlint.org/mcp and call validate_vast, validate_vast_url, inspect_vast, list_rules, explain_rule, or fix_vast. Each tool returns structured JSON with rule IDs, XPath locations, and spec references.

From the project README, punctuation lightly normalized. Full text: https://raw.githubusercontent.com/aleksUIX/vastlint/HEAD/README.md

## Skills

- inspect-vast: Follow a VAST wrapper chain hop by hop with inspect_vast. Use when the user has a tag URL, asks why a wrapper fails, mentions error 303, VASTAdTagURI, or wrapper depth, or wants AdSystem, Duration, and media files per hop.
- validate-vast: Validate VAST, VMAP, or DAAST XML or a live tag URL against IAB Tech Lab specs using vastlint MCP tools. Use when the user pastes a tag, gives a VAST URL, asks if a tag is spec-valid, or wants rule IDs and fixes.

Descriptions come from the frontmatter of each SKILL.md, punctuation lightly normalized.

## MCP servers

- vastlint: transport: streamable-http; url: https://vastlint.org/mcp

Read from the plugin's own mcp.json. Environment variable names only, never values.