Catalog (freely callable)

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

Annotations already establish read-only, idempotent, non-destructive behavior, and the description adds substantial context on top: upstream omits discontinued variants, index fields may be null, next_offset/has_more pagination semantics, and that textual clipping at 120 chars flags malformed upstream data. This is exactly the kind of beyond-annotation disclosure the dimension rewards.

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-loaded with purpose and overall well organized, but the long enumeration of variant fields (sizing_system, load_index, dual_load_index, speed_index, etc.) is dense and partly redundant with the output schema that already exists. Efficient but not maximally tight.

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 an output schema exists, return-field explanation is optional, yet the description still covers nullability, unit conventions for metric vs flotation variants, discontinuation gaps, and pagination caveats. Nothing an agent needs to call this correctly is missing.

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 brand, product, limit and offset are already fully documented, including the 1–50 range and 0-based offset. The description reinforces the next_offset/has_more flow but adds no new syntax or constraint beyond the schema, so the baseline of 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 and resource — 'List the known current size variants of one model in the catalog' — which cleanly separates it from siblings like tires_list_brand_tires (all tires of a brand) and tires_get_tire (single tire detail). An agent can route to it without opening the 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?

Explains interpretation scope ('proves recorded size availability for a model, not warehouse stock and not vehicle fitment') and gives pagination guidance ('follow next_offset while has_more; a short first slice does not prove a size is absent'). It does not name an alternative sibling to use when the agent actually wants stock or fitment data, so it stops short of full when/when-not routing.

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