Tomorrow Lives Engines

Read a pre-registration

pull_prereg

Read-onlyIdempotent

Reads a pre-registration (what is measured, the conditions, trials per session, sessions, alpha, power, the number of comparisons and the correction) and returns its hash, to record in each session's prereg.hash before the run starts. Costs no units.

Input Schema

Name	Required	Description	Default
`prereg`	Yes	The pre-registration document, written inline as JSON; pull_schema lists its keys.

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 / prereg / description

Added value: +"The pre-registration document, written inline as JSON; pull_schema lists its keys."

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 declare readOnly, idempotent, non-destructive, and closed-world behavior. The description adds useful behavioral context beyond those: it explicitly states the operation costs no units and returns a hash.

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, front-loaded sentence with an informative parenthetical. Every clause earns its place, and nothing is wasted.

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

Completeness5/5

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

Output schema exists so return-value details are not required, yet the description still names the returned hash. With annotations covering safety and the input schema covering structure, the definition is complete for correct invocation.

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

Parameters4/5

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

Schema coverage is 100% and the schema defers key listing to pull_schema. The description adds meaning by enumerating what the prereg object contains (measures, conditions, trials, sessions, alpha, power, comparisons, correction), which helps an agent understand the parameter without a separate schema call.

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

Purpose4/5

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

States a specific verb (reads) and resource (pre-registration) and clarifies the return value (its hash). It does not explicitly differentiate itself from sibling pull_* tools, so it falls short of a 5.

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?

Gives a clear usage context: record the returned hash in each session's prereg.hash before the run starts. No alternatives or when-not conditions are named, which keeps it from a 5.

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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