Tomorrow Lives Engines

Check a print design

art_check

Read-onlyIdempotent

Checks a design without rendering it: ok, or one sentence naming the first problem and where it is. Costs no units.

Input Schema

Name	Required	Description	Default
`design`	Yes	The print design document, written inline as JSON. art_schema lists every key.

Output Schema

Name	Required	Description
`ms`	No	Milliseconds the run took.
`job`	Yes	The job id; the job tool reads it.
`verb`	No	The tool that made it.
`files`	No	Files made, each with a name, type, size and a signed URL.
`units`	No	Units this call cost.
`result`	No	The engine's own answer, a JSON document.
`status`	No	queued when the job runs in the background.

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedOct 14, 2026

addedInput schema / properties / design / description

Added value: +"The print design document, written inline as JSON. art_schema lists every key."

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": true,
+  "properties": {
+    "files": {
+      "description": "Files made, each with a name, type, size and a signed URL.",
+      "items": {
+        "additionalProperties": {},
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "job": {
+      "description": "The job id; the job tool reads it.",
+      "type": "string"
+    },
+    "ms": {
+      "description": "Milliseconds the run took.",
+      "type": "number"
+    },
+    "result": {
+      "description": "The engine's own answer, a JSON document."
+    },
+    "status": {
+      "description": "queued when the job runs in the background.",
+      "type": "string"
+    },
+    "units": {
+      "description": "Units this call cost.",
+      "type": "number"
+    },
+    "verb": {
+      "description": "The tool that made it.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "job"
+  ],
+  "type": "object"
+}

First observedOct 14, 2026

TDQS

A4.2/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover read-only/idempotent/non-destructive/closed-world, and the description adds genuinely new behavior: no rendering occurs, it returns 'ok' or exactly one sentence naming the first problem and its location, and it consumes no units. That cost/side-effect disclosure is exactly the kind of context annotations cannot express.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

A single sentence with a colon-delimited result spec; the most decision-relevant fact (no rendering, no cost) is front-loaded and every clause earns its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With a rich output schema and fully documented annotations, the description only needs to add cost and validation semantics, which it does. It could be slightly stronger by noting where a valid design document comes from (e.g. art_starter/art_schema), but nothing needed to invoke it correctly is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

There is one parameter and schema coverage is 100%, with the schema itself pointing to art_schema for the document keys. The description adds nothing about the 'design' argument, so the baseline 3 for high schema coverage applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (checks) and resource (a design), and immediately delimits scope with 'without rendering it', which cleanly separates it from art_render and the other *render siblings. An agent can tell what this does and what it does not do without opening the schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

'Costs no units' gives a clear economic reason to call this before art_render, which is an implied when-to-use cue. It stops short of naming art_render explicitly or stating exclusions, so it is clear context rather than a full routing rule.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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