list_model_instances

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

There are no annotations, so the description alone must disclose behavior. 'List' implies a read-only operation, but the description does not mention pagination, output shape, authorization, or the effect of page_size. This is below the minimum viable level for a tool with no annotation support.

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 a single front-loaded sentence with no filler and gets the main action across immediately. It is concise, though 'instances/variations' could be more precise.

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 and no annotations, the description must carry more weight. It omits pagination semantics, required authentication, and the expected return representation, and it does not compensate for the empty parameter descriptions, so it is not sufficient for reliable invocation.

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 descriptions are all empty (0% coverage), and the description adds only the clue that model_ref is an owner/model identifier. It does not clarify the expected format of model_ref or the meaning of page_size beyond the schema's default and type, leaving a required parameter under-documented.

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 names a concrete verb ('List'), a resource ('model instances/variations'), and the scope ('for owner/model'), so an agent can tell this is a listing operation scoped by an owner/model identifier. It does not explicitly distinguish this from the sibling list_model_instance_versions or get_model_instance, and the word 'variations' is somewhat ambiguous, so it falls short of a top score.

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?

'List ... for owner/model' implies the tool should be used when fetching all instances/variations for a given model, but it offers no explicit guidance about when to prefer the many sibling tools, such as get_model_instance or list_model_instance_versions. There is no when-not-to-use guidance or alternative selection criterion.

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