add_material_function_call

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

Annotations already declare this is a non-read-only, non-idempotent, non-destructive edit. The description adds genuinely useful behavior beyond that: the failed-call case is atomic ('Refused, with the node removed again'), and the pin-binding semantics of the created node are disclosed. Only permission/auth context and explicit non-idempotency wording are absent.

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 sentences plus a compact return shape, all front-loaded with the action first and the caveat second. With no output schema present, the Returns line earns its place rather than being 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 graph-mutation tool with full annotation coverage and full schema coverage, the description covers the action, the failure mode, and the return payload. It stops short of situating itself against the closely-named material-function siblings, which is the one remaining gap.

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 all three parameters (material_path, function_path, node_name) are already documented with examples and the unique-name fallback. The description adds no syntax or path-format detail beyond that, 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 ('Insert a call to a UMaterialFunction into a UMaterial graph') and then pins down the resulting object ('a MaterialFunctionCall node bound to the function, so the function's inputs and outputs become the node's pins'). This is enough to separate it from siblings such as add_material_function_input/add_material_function_output, which act on the function asset rather than a graph.

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 purpose strongly implies when to reach for it (you want a material function called inside a material graph), but there is no explicit when/when-not guidance and no named alternative among the many material-function siblings. The refusal condition is a behavioral note, not usage routing.

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