spine_update_slot

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

With no annotations, the description carries real weight and mostly delivers: it discloses partial-update semantics ("Only the arguments you pass are changed"), that renaming cascades to skins, animations, draw-order keys and path constraints, and that empty strings act as clear/reset sentinels. It omits error behavior (what happens if the slot or project is unknown) and any permission or validation constraints.

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?

Two lead sentences establish what the tool does and how partial updates behave, then a compact argument list; every line adds distinct information with no repetition of schema titles.

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?

An output schema exists, so return values need not be described, and the parameter semantics are well covered. What remains thin is failure behavior — whether an unknown slot name or invalid bone produces an error versus a silent no-op — which matters for a mutation tool with zero annotation coverage.

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 do all the work, and it documents seven of nine parameters with formats and edge cases: RRGGBB(AA) color encoding, the "" clear/reset semantics for attachment, color and dark, the blend mode enumeration, and draw-order indexing (0 = back). The two undocumented parameters are the required project and slot name identifiers, which are self-evident from schema titles.

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?

"Change an existing slot" gives a specific verb and resource, and the sibling set makes the add/update distinction (spine_add_slot vs spine_update_slot) inferable. It does not name an alternative outright, so it stops short of a 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?

Usage is implied by "Change an existing slot" plus the patch semantics line, which tells the agent this modifies in place. There is no explicit statement of when to prefer this over spine_add_slot, and no mention of preconditions such as the slot already existing.

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