add_shape_key

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

With no annotations, the description explicitly discloses a non-obvious side effect: 'The first call also creates the Basis,' and it describes the blending parameter's semantics. It also documents the return shape ('Dict with the new key and every key on the object'), which is important for a mutation tool with no readOnly/destructive annotations.

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 content is front-loaded with the core action and the Basis side effect, then the workflow routing and parameter documentation. The multi-line layout is appropriately structured for clarity rather than padding.

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 tool with 0% schema coverage and no annotations, the description covers the action, side effects, parameter meanings, sibling workflows, and return value. An output schema exists, so return-value phrasing is reinforced rather than required, but the description stands on its own.

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 0%, so the description must carry all three parameters; it does so: object_name ('Mesh object'), key_name ('Name for the new key'), and from_mix ('Start from the current blend of all keys instead of the Basis'). The from_mix explanation adds the meaning of the default false, which the schema does not.

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 specific verb and resource ('add a shape key (blend shape)') and immediately distinguishes this from the other shape-key siblings by assigning each a role (move, blend, animate). It also defines what a shape key is in Blender terms, so an agent can distinguish add from remove/set/keyframe without opening another schema.

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 provides explicit workflow guidance: 'Shape it with move_shape_key_vertices, blend with set_shape_key, animate with keyframe_shape_key,' routing the agent to the correct sibling tools. It also explains the alternative parameter (from_mix) for starting from the current blend. The only omission is an explicit 'don't use if X' exclusion, but the scope is otherwise clear.

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