characters_list

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

The annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=false, so the safety profile is fully covered. The description contributes the useful scope fact that results are limited to 'the current scene' and hints at the returned fields (owner IDs, joint counts). Since there is no output schema, it could say more about the shape of the result, but what it offers is legitimate added 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?

A single short sentence with no filler; the scene-scope constraint and the returned data are packed in without redundancy.

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 parameterless read with annotation coverage and no output schema, the description supplies the essential scope and the key returned fields. It stops short of explaining what a 'RigInfo owner ID' identifies in practice or how a caller should use the joint counts, which leaves a nontrivial conceptual gap for an agent new to the rig tooling.

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 tool takes zero parameters and the schema is trivially empty, so there is nothing for the description to disambiguate. Per the zero-parameter baseline this scores a 4.

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 names a concrete payload — 'RigInfo owner IDs and Joint membership counts' — but the verb 'Discover' is vague about what the tool actually is (an enumeration of characters in the scene). It never explicitly says this is a list/enumerate operation, nor does it separate itself from nearby tools like objects_list, character_skeleton, or rig_semantics.

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?

There is no indication of when to call this versus the many sibling enumeration tools (objects_list, rig_profiles_list, character_skeleton, rig_semantics) or whether it should be called before rig_pose_apply / rig_profile_read to obtain the required owner IDs. Usage is left entirely to inference.

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