List actors in the world (name, type, ID), at most 200 rows. For anything beyond a plain listing — by name, CR, creature type, size, folder, HP, AC — use actor-filter, which also paginates. Actor IDs are needed for rolls, combat, items, and effects.
| Name | Required | Description | Default |
|---|---|---|---|
| type | No | Filter by type: "character", "npc", "vehicle", or system-specific types |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, covering the safety profile. The description adds valuable behavioral context beyond that: the row limit ('at most 200 rows') and the scope ('in the world'). It also implies the limitation that only name, type, and ID are returned, which is useful for downstream needs.
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?
The description is two sentences, each earning its place. The first sentence front-loads the core purpose and row limit. The second sentence gives usage guidance and a practical note about actor IDs. No filler or redundancy.
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 simple listing tool with one optional parameter and no output schema, the description covers all essential aspects: what it returns, the row limit, the alternative tool, and why the results matter (actor IDs for rolls, combat, items, effects). Nothing an agent needs 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.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100% for the single optional 'type' parameter, so the schema already explains its meaning and allowed values. The description does not add any parameter-specific detail, but it doesn't need to since the schema fully documents it. The baseline of 3 applies: the description neither enhances nor detracts from parameter understanding.
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 states a specific verb ('List'), a clear resource ('actors in the world'), and the returned fields (name, type, ID). It also explicitly differentiates itself from actor-filter by naming exactly what actor-filter handles ('by name, CR, creature type, size, folder, HP, AC'). This is a precise, unambiguous purpose statement.
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 description gives explicit guidance: 'For anything beyond a plain listing — by name, CR, creature type, size, folder, HP, AC — use actor-filter, which also paginates.' This names the alternative and the exact conditions for selecting it, leaving no ambiguity about when to use this tool versus its sibling.
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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