add_material_expression

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

With no annotations, description fully specifies safety ('without clearing') and return value (node_index). Details required fields for Custom HLSL nodes. Omits error scenarios and permission requirements, but core behaviors are transparent.

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?

Three sentences with example JSON; no redundant words. Purpose front-loaded, followed by return value, next step, and parameter details. Every sentence earns its place.

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?

Covers the core functionality well; node parameter is fully described. Does not explain material_path, but the context of sibling tools and common pattern mitigates this. Output schema exists, so return format is covered elsewhere.

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 has 0% coverage, but description adds full parameter semantics: the node parameter is a JSON object with type, pos_x, pos_y, properties, plus optional fields for Custom HLSL. material_path is not elaborated, but the example style implies it's a path string.

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 'Add a single expression node without clearing other nodes,' clearly identifying the verb (add), resource (expression node), and key behavior (no clearing). Distinguishes from siblings like delete_material_expression and connect_material_expressions.

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 says to wire up with connect_material_expressions after adding, providing immediate next-step guidance. However, lacks explicit when-to-use vs alternatives and does not mention prerequisites or excluded use cases.

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