Tomorrow Lives Engines

Check a world

world_check

Read-onlyIdempotent

Checks a world document with the engine's strict reader and its spatial rules (every spawn, passage, item and character stands on open ground reachable from the spawn; no two zones overlap; no door is under water). Answers ok with warnings, or the errors; the doors report says how many exits were examined. Costs no units.

Input Schema

Name	Required	Description	Default
`world`	Yes	The world document, written inline as JSON.

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 / world / description

Added value: +"The world document, written inline as JSON."

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

A3.9/5.0

Behavior4/5

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

Annotations already declare the read-only, idempotent, non-destructive profile, but the description adds real behavioral context: what spatial invariants are enforced, that results come back as ok-with-warnings or errors, that a doors report counts exits examined, and that it consumes no units. It stops short of describing warning severity or failure modes in depth.

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

Conciseness4/5

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

Two sentences, front-loaded with the verb and the validated rules, followed by the return shape and cost. The parenthetical rule list is dense but informative rather than padding, though it could be trimmed slightly.

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 annotations covering safety, an output schema handling return structure, and 100% schema coverage, the description supplies the remaining essentials: the checks run, the warning/error outcome, and zero cost. Only a clearer when-to-use cue 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?

Only one parameter, and schema coverage is 100% — the schema already documents 'world' as an inline JSON document. The description adds nothing about the parameter's shape or format beyond what the schema states, so the baseline 3 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 world document), and enumerates the exact validations performed — spawn/passage/item/character reachability, zone overlap, doors under water. This cleanly separates it from siblings like world_apply (mutates) and world_schema (schema description), so an agent can pick it without opening a schema.

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

Usage Guidelines3/5

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

The line 'Costs no units' implies this is a cheap pre-flight check worth running freely, which hints at usage. But it never states when to reach for world_check versus world_schema or before world_apply, and gives no exclusions, leaving the workflow to inference.

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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