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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds value by explaining the per-leg allowlist structure and how ruleset omission changes the result scope. This is meaningful behavioral context beyond the annotations, with no contradiction.

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?

Two sentences with no filler: the first states the core purpose, the second explains the optional parameter behavior. Every sentence earns its place and the description is immediately scannable.

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 read-only list operation with only two parameters, full schema coverage, an output schema, and strong annotations, the description covers the only non-obvious behavior (leg-scoping). Nothing needed for correct invocation 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%, and the schema's ruleset description already conveys the union-vs-scoped behavior. The tool description repeats this nuance but adds no new parameter-level information, so the 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 states a specific verb ('List') and resource ('items the campaign DM has added to the campaign's allowlists'), and distinguishes itself from the broader vault catalog by calling itself a 'Subset'. This clearly differentiates it from sibling item-related tools like vault_search_items or play_add_campaign_item.

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 explains the key conditional behavior of the `ruleset` parameter (omit to union across legs, set to scope to one leg), which tells the agent when to use the tool with or without that parameter. It does not explicitly name alternative tools or state when not to use it, but the per-leg scoping guidance provides clear practical usage context.

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