mmar_create_scene_instance

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

With no annotations, the description carries the full burden. It does add valuable behavioral instructions, such as generating a new UUID v4 and enumerating optional arrays within scene_instance_data. However, it does not disclose side effects like session requirements, validation behavior, or what the tool returns, leaving some uncertainty.

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?

The description is two sentences: the first states the tool's purpose, and the second explains the required data structure. It is front-loaded, concise, and contains no irrelevant information.

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?

Given the absence of an output schema and annotations, the description covers the core purpose and input requirements effectively. It lacks an explicit mention of return values or potential errors, but the essential information for invoking the tool is present.

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?

The schema already covers both parameters with 100% description coverage. The description goes beyond this by explicitly listing the optional arrays (class_instances, relationclasses_instances, role_instances, attribute_instances, port_instances) and instructing the agent to generate a new UUID v4, adding meaningful semantic detail.

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?

The description uses a specific verb+resource phrase: 'Create a new model instance (diagram) for a specific SceneType.' It clearly differentiates this from creating a SceneType or other instance types by specifying 'model instance' and 'for a specific SceneType.'

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 description provides clear context: it is for creating a new scene instance for a given SceneType, which implies when to use it. However, it does not explicitly mention alternatives or exclusion criteria, like 'use this when creating a diagram instance rather than a scene type.'

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