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

Annotations already declare readOnly/idempotent/non-destructive, and the description goes well beyond by disclosing default response shape, the ownership distinction between `owner` and `characterOwner` (including edit rights), that `status` reflects the seat's state, and that `companionIds` enumerates Owned companions seated with the character. That is substantial behavioral context not available from structured fields.

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?

Front-loaded with purpose and zero filler; every clause carries a semantic payload. Some sentences are dense run-ons about ownership and seats, but nothing is redundant with the schema or annotations.

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 2-param read tool with full schema coverage, annotations, and an output schema, the description covers everything an agent needs: what it lists, response shape options, and the meaning of the less-obvious returned fields. Return-format detail is appropriately delegated to the 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 baseline is 3, but the descriptionadds practical meaning to `detail` by enumerating the summary fields (id, name, image, npc flag, short description) and clarifying 'full' returns the vault sheet inline. campaignId gets no added meaning, but the enriched enum guidance lifts this above baseline.

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 and resource with scope: 'List the characters participating in a play campaign.' It distinguishes itself from vault_get_character by noting it returns play-side refs rather than full sheets, though it never explicitly contrasts with close siblings like play_list_campaign_players or play_list_campaign_companions.

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 actionable routing: pair with vault_get_character for full data, or pass detail: 'full' to get sheets inline. It also clarifies who may edit (characterOwner or admin with Admin Mode) via vault_update_character. No explicit 'when not to use' statement, but the alternatives are named with conditions.

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