list_entitiesCharacters, props, places; ref ids are generate_video reference_image_ids. -@slug in a prompt leaves one out; @slug/alone drops its items. Free.
| Name | Required | Description | Default |
|---|---|---|---|
| id | No | One entity in full: refs, sheet (prefer sheet.asset_id as a ref), looks, links, facets, bio, voice, specs (a prop's or place's facts by stable key, e.g. top_speed). | |
| kind | No | skin = an outfit with its accessories, reusable on anybody. |
Changes observed during successful MCP inspections.
Input schema / properties / id / descriptionPrevious value: -"One entity in full: refs, sheet (prefer sheet.asset_id as a ref), looks, links, facets, bio, voice."New value: +"One entity in full: refs, sheet (prefer sheet.asset_id as a ref), looks, links, facets, bio, voice, specs (a prop's or place's facts by stable key, e.g. top_speed)."Input schema / properties / idAdded value: +{
+ "description": "One entity in full: refs, sheet (prefer sheet.asset_id as a ref), looks, links, facets, bio, voice.",
+ "type": "string"
+}Input schema / properties / kind / descriptionAdded value: +"skin = an outfit with its accessories, reusable on anybody."Input schema / properties / kind / enumPrevious value: -[
- "character",
- "prop",
- "location",
- "look"
-]New value: +[
+ "character",
+ "prop",
+ "location",
+ "look",
+ "skin"
+]Input schema / properties / kind / enumPrevious value: -[
- "character",
- "prop",
- "location"
-]New value: +[
+ "character",
+ "prop",
+ "location",
+ "look"
+]Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
readOnlyHint=true already covers the safety profile, and the description adds beyond that: ref ids map to generate_video reference_image_ids and the operation is 'Free'. It does not mention pagination or return shape, so it clears the lowered annotation bar without being exhaustive.
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?
Compact and front-loaded: resource types first, then the ref-id and @slug semantics, then cost. No filler, though the '@slug/alone' phrasing is terse enough to be ambiguous.
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 read-only list tool with full schema coverage and readOnlyHint, the description supplies the missing context (what the ids are for, prompt syntax, cost). Only the list output format is left unspecified, which is a minor gap given no output schema.
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 coverage is 100%, so both id and kind are already fully documented in the schema, including the skin enum meaning. The description adds the reference_image_ids linkage but does not elaborate on the two parameters themselves, so baseline 3 is appropriate.
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?
The description enumerates the resource types it covers (characters, props, places) and ties them to generate_video ref ids, so the agent understands this is the reusable-entity lister. It is clear but stops short of an explicit verb like 'list all entities' and does not name a sibling it differs from.
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?
The '@slug' notes and 'Free' hint give usage context for consuming these entities in prompts, but there is no explicit when-to-use versus alternatives (e.g. list_assets). Usage is implied through the generate_video ref-id linkage rather than stated as guidance.
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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