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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds value beyond them: 'without saving or starting paid generation' confirms no cost or side effects, and 'Return diagnostics and normalized settings' describes the outcome even though no output schema exists. It does not cover rate limits or auth requirements, keeping it short of a 5.

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

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

Purpose and no-side-effect guarantee are front-loaded, followed by contract details. It is dense and reads partly like reference documentation packed into one paragraph, but nearly every sentence carries actionable content.

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

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

For a tool with 0% schema coverage, no output schema, and untyped 'project'/'definition' parameters, the description supplies the missing contract context, points to the SDK and existing-definition sources, and states the return shape. Nothing an agent needs to invoke it correctly appears absent.

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

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

Schema description coverage is 0% across 8 parameters, so the description carries the full burden. It supplies rich domain semantics (input types, handledInputBindingIds, overlay region fractions, Genesis.action, onEvent(context)) but rarely maps them to parameter names; 'project', 'definition', 'interfaceSource' vs 'interfaceFiles', and 'previewImageUrl' remain ambiguous. Above baseline but not fully compensating.

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

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

States a specific verb and resource ('Validate a complete experience definition and optional custom interface code') plus scope ('without saving or starting paid generation'), which separates it cleanly from save_world_experience and validate_world_code_workspace. An agent can identify what this does 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.

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

Explicitly routes the agent to prerequisite sources: 'Use the existing definition contract from get_world_experience or list_world_experiences' and 'Read get_genesis_sdk for the exact contract and examples.' It implies the validate-before-save workflow but never explicitly states when NOT to use it (e.g., versus save_world_experience or validate_world_code_workspace).

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