create_material_expression

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

Annotations only declare this is a non-read-only, non-idempotent mutation. The description adds critical behavioral context beyond that: the node arrives UNCONNECTED, nothing renders until wired, and the success flag is not sufficient verification. This disclosure meaningfully changes how an agent uses and validates the tool.

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 core action, then the workflow, then the return shape. Every sentence earns its place, and the return block is justified because no output schema exists. It is dense but well-organized.

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?

With no output schema, the description supplies the return shape and types, and with annotations only covering the mutation profile, it also supplies the unconnected-node caveat and verification path. An agent has everything needed to call and validate the tool correctly.

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 documents all four parameters, setting a baseline of 3. The description adds real value by enumerating example expression class paths (Constant, TextureSample, ScalarParameter) and clarifying the position parameter, which helps an agent form a valid call.

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 ('Add ONE node to a material graph'), plus the scoping ('by expression class path ... at a graph position') and clarifies it is a single-node operation. It is easily distinguished from sibling material tools like create_material_function_expression or duplicate_material_expression.

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?

Explicitly frames the tool as the building block of a workflow ('create the nodes, then wire them with connect_material_expressions and connect_to_material_output') and names verification alternatives (get_material_expressions, get_material_stats) with the condition for using them. Nothing is left to inference.

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