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

Annotations carry little signal (all hints false), so the description carries the full burden — and it delivers. It discloses detailed gateway behavior: computing stored base values from source-text values, deriving proficient/expertise/misc flags, formatting spell-list markdown, creating recharge trackables, generating Challenge/Legendary Actions/Speed-alternate-form notes, and automatically setting `type`, `settings.autoPassiveBonuses`, and `core.experience`. This is far beyond what annotations provide.

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 long but dense, with every sentence adding information: purpose, differentiation, gateway behavior, automatic settings, authoring guide pointer, and return value. It is front-loaded with the core purpose and follows with operational details. No filler or tautology.

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 tool's complexity (31 parameters, nested objects, 10 required fields) and an existing output schema, the description covers all decision-relevant aspects: what to pass, how the gateway transforms it, where to find the authoring guide, what gets set automatically, and what is returned. Nothing an agent needs to correctly invoke this tool 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%, so the baseline is 3. The tool description adds a key cross-cutting semantic: 'Caller passes source-text values (final AC, skill bonuses, attack bonuses); gateway computes the stored base values.' This clarifies the intent behind every numeric field and explains how the gateway transforms input. It doesn't enumerate parameters individually, but the schema already does, making the description a valuable supplement rather than a replacement.

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 opens with a specific verb and resource: 'Create a complete 5e24 monster character in one call.' It then explicitly distinguishes itself from the sibling pattern (`vault_create_character` + multiple `vault_update_character`) by stating it replaces that pattern for monster authoring. This immediately disambiguates it from vault_build_pc and other character-related tools.

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 clearly states when to use this tool — for monster authoring — and names the alternative pattern it replaces. It also gives a ruleset exclusion: 'Other rulesets will land via their own build tools.' Additionally, it points to `vault_get_authoring_guide` as the conventions reference, telling the agent where to get authoritative instructions on field shape.

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