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

Annotations already establish the safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=false), so the bar is lower; the description goes beyond them by disclosing a non-obvious server-side side effect — memberNpcEntryIds are projected into MEMBER relationships — plus the GM/co-GM auth requirement. It stops short of covering failure modes, visibility defaults, or the 50-item batch limit, so not 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?

Three short sentences, each carrying distinct load: purpose, key parameter behavior, authorization. Front-loaded with the verb and resource. Minor waste in the parenthetical examples, but overall tight.

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?

An output schema exists, so return values need no explanation. For a create tool with nested items, the description covers purpose, the member-projection behavior, and auth — enough to call it correctly. It omits visibility defaults, batch-size limits, and the required campaignId context, hence a minor gap.

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?

Top-level schema coverage is 0% (only nested item fields carry descriptions), so the description must compensate. It does explain memberNpcEntryIds semantics and its relationship side effect, but says nothing about the required campaignId, the items array/batch shape, or the visibility and relationshipIds fields.

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+resource ('Create Faction mnemons') and immediately clarifies the domain with parenthetical examples (factions, guilds, cults, companies), which separates it from the many sibling create_*_mnemons tools that target NPCs, quests, lore, etc. An agent can pick this over create_npc_mnemons or update_faction_mnemon without opening a 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?

Gives a clear authorization precondition ('Players may not call this — GM/co-GM only'), which materially affects whether an agent should invoke it. It does not, however, point at the alternative for editing an existing faction entry (update_faction_mnemon) or state when-not conditions such as duplicate titles.

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