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

The description goes beyond the annotations by disclosing that system data is DEEP-MERGEDholistically: untouched paths remain intact but arrays are replaced entirely. This is useful behavioral context that the schema and annotations alone do not provide. It does not mention permissions or errors, but the core mutation behavior is well disclosed.

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 two sentences that front-load the operation and resource, follow with critical merge semantics, and end with a practical example. There is no filler or redundancy; every clause 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?

With all parameters documented in the schema and the description covering the complex nested-object merge behavior, an agent has enough information to make a correct call. The absence of an output schema and no statement about the return value or error behavior is a minor gap, but it does not block successful 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?

Schema coverage is 100%, so the baseline is 3, but the description adds genuine meaning beyond the schema by explaining the deep-merge behavior and providing a concrete dnd5e path example. The common-path listing also helps agents construct valid system inputs, which the schema alone only hints at.

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 verb ('Update'), the resource ('an actor'), and the specific fields affected (name, image, folder, system data). It does not explicitly name sibling alternatives like actor-create or actor-delete, but the 'update' verb conveys the operation distinctly enough.

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 clear usage context: use this tool to mutate an existing actor's top-level fields or system data, with explicit guidance to pass only changed paths. It does not explicitly say when not to use it or name alternatives, so it lacks exclusions, but the intended context is unambiguous.

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