add_rig_null

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

Annotations already declare readOnly=false, idempotent=false, destructive=false, openWorld=false, covering the core safety profile. The description adds essentially nothing behavioral of its own — it doesn't state that the change is written to disk automatically, whether it can fail, or any auth/undo implications (the 'saved'/'save_error' fields hint at persistence but are not explained).

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?

Front-loaded with a single clear sentence, then a Returns block. The Returns block is somewhat verbose, but since there is no output schema it earns its place by documenting the response shape; overall there is little wasted text.

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 an add-element mutation tool with a 100%-covered schema and full annotations, the description's main job is done: purpose and return shape are both given, compensating for the absent output schema. It could still say the rig is saved to disk on success, but nothing essential for invoking the tool correctly 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 schema fully documents all six parameters, including the detailed PIE-refusal caveat on force. Per the baseline rule, 3 is the correct score when the schema does the heavy lifting and the description adds no additional parameter meaning.

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 states a specific verb and resource ('Add a null (space) to a Control Rig's hierarchy'), so the operation is unambiguous and distinguishable from siblings like add_rig_bone or add_rig_control by the resource noun. It stops short of explicitly contrasting those siblings or noting the parent/parent_type placement options, so 4 rather than 5.

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 offers no when-to-use guidance, no prerequisites (e.g. the rig asset must exist/open), and no alternatives or exclusions. The only contextual guidance in the entire definition lives in the force parameter's schema text, not the description, so the description itself provides no routing help.

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