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

Annotations declare this is a non-read-only, non-idempotent, non-destructive creation that stays within the world (openWorldHint=false). The description adds that 'system is deep-merged over the defaults', which explains how partial system data is handled — genuine context beyond the annotations. It stops short of disclosing validation errors, required permissions, or what a successful create returns, 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?

Compact and front-loaded: the core action and examples come first, followed by type constraints, the sibling pointer, and the merge behavior. The type enumeration is a bit dense inline, but every sentence carries information an agent needs before calling.

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 creation tool with no output schema and full schema coverage, the description supplies the missing decision context: the sibling alternative, per-system type values, and merge semantics. Minor gaps remain around whether creation triggers sheet initialization or defaults, but nothing essential to a correct call is absent.

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 the baseline is 3, but the description adds real value: the type enum is expanded per game system (including pf2e types like hazard, loot, familiar, army that aren't in the schema text), and it explains that the type 'must fit the game system'. It also clarifies the deep-merge semantics of the system parameter, which the schema leaves as a bare 'additionalProperties' object.

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 ('Create an actor from scratch') and enumerates concrete examples (custom NPCs, characters, creatures). It also explicitly distinguishes itself from the sibling actor-create-from-compendium, leaving no ambiguity about which tool builds an actor manually.

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 an explicit alternative for creating from a compendium monster ('actor-create-from-compendium') and lays out the valid type values per game system (dnd5e, pf2e). The agent knows both when to use this tool and which argument values are legal.

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