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

The description goes well beyond the annotations by disclosing that the server fills per-ruleset sheet skeletons, that minimal create calls match web/iOS client output, that the character is owned by the calling user, and that linked-campaign characters should be modified with care. This is rich, non-obvious behavioral context.

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 front-loaded with the core action and then efficiently covers requirements, server behavior, minimal-body equivalence, monster creation, ownership, and a safety caveat. Every sentence adds useful information without repetition or filler.

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?

With an output schema present, return-value documentation is unnecessary. The description covers inputs, creation behavior, ownership, and linked-campaign caution. It is slightly incomplete in not differentiating from vault_build_pc/vault_build_monster or explaining which ruleset values are valid, but overall it is sufficient 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 schema exposes zero properties, so the description carries the parameter burden. It names the required parameters (`name`, `ruleset`), explains their necessity, and documents the `type: "monster"` special value. It could define valid ruleset formats or richer-structure shapes, but the baseline for zero schema parameters is met and meaningfully exceeded.

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 clearly states the action ('Create a new character'), the target resource ('in the user's vault'), and the required minimal inputs. It distinguishes itself from vault_create_item/spell/rule and build-oriented siblings by specifying the character creation scope and the optional monster type marker.

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 concrete context: minimal bodies work, richer structures can be passed inline, and monster creation is signaled with type: 'monster'. It does not explicitly enumerate when to choose this over vault_build_pc or vault_build_monster, but the use case is clear and no misleading guidance is present.

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