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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the bar is lower. The description adds genuinely new behavioral context: image URLs are opt-in via include_image_url, and search is hybrid across names, metadata, and visual attributes. It does not describe return shape or pagination behavior, but that is a modest gap given the annotation coverage.

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 tight sentences, front-loaded with the core action and disambiguation before the capability notes. No filler or restated title text; every clause carries 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?

For a zero-required-parameter list tool with 100% schema coverage and safety annotations, the description covers identity, routing, search modes, and the key opt-in flag. It does not mention result volume/pagination behavior, a minor omission since no output schema exists.

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 already documents all nine parameters including defaults and constraints. The description reinforces query and include_image_url semantics but adds no syntax or format detail beyond what the schema already states, so 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 (List) and resource (the user's Models/avatars), and immediately disambiguates the ambiguous term 'Model' from AI models by naming the sibling mcp_list_model_catalog. An agent can route correctly without opening either schema.

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 names the alternative (mcp_list_model_catalog) and the condition that selects it ('for those [AI models]'), plus states the two search modes (structured filters vs. hybrid query) and when to set include_image_url=true. Both the when-to-use and the sibling alternative are covered.

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