material_assign

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

With no annotations, the description carries the full burden and does well: it discloses the propagation side effect (an occurrence inherits its component's material, affecting all occurrences), the ambiguous-name error payload, and the returned "previous" value that implies replacement of any existing assignment. It stops short of stating units for density/mass or whether the change is undoable/persisted beyond the presence of "previous".

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-loads the verb and targets, then layers in the occurrence caveat, id sourcing, error behavior, verification step, return shape, and a concrete example, each in its own short block. No sentence is filler.

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?

There is no output schema, so the description supplies the exact return payload (target, applied_to, material, previous, plus note for occurrences), which is what an agent needs to chain calls. Combined with the ambiguity-error and follow-up-verification guidance, nothing essential is missing for a 3-parameter mutation tool.

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% and all three parameters are documented there, including library's ambiguity-resolution purpose. The description reinforces that material should be an id from material_list (preferred) or an exact name, but adds little beyond what the schema already states, so the baseline 3 applies.

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?

States a specific verb and resource ("Assign a physical material") and scopes the valid targets (body, component, occurrence). The parenthetical "(density, mass)" cleanly separates it from the appearance_* siblings, and it names material_list as the id source, so an agent can distinguish it without opening the 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?

Gives explicit preconditions (take the id from material_list), the failure/alternative path (ambiguous name fails with details.candidates; use the library parameter), and a follow-up step (verify mass with inspect_physical_properties). It also states the occurrence special case, so when-to-use and what-to-do-next are both covered.

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