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

With no useful annotations (all false), the description carries the burden. It discloses that caller authorization is via campaign 'contribute' permission and that fields pass through to play. It doesn't mention return values or side effects beyond creation, but the output schema covers that. This adds meaningful context beyond the empty annotations.

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, no fluff. Purpose is front-loaded, then required/optional fields, then permission note. Every sentence earns its place.

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?

Given the empty schema and existing output schema, the description covers all necessary calling details: purpose, required fields with format, optional fields, and authorization. No critical information is missing for correct invocation.

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?

The input schema is empty ({}), so the description is the sole source of parameter information. It lists required parameters (campaignId, date) with date format, and optional ones (name, description, planned battlemaps). This fully compensates for the schema gap and adds precise semantics.

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 and resource: 'Create a new session for a campaign.' This clearly distinguishes it from siblings like play_create_campaign, play_create_move, or play_delete_session. The purpose is unambiguous and front-loaded.

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 implies its use case (creating a session for a campaign) and specifies required vs optional fields, but it does not explicitly contrast with alternatives such as play_update_session. The necessity is clear from context, but explicit exclusion of when-not-to-use is absent.

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