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

Annotations already declare readOnly/non-destructive/openWorld=false, yet the description still adds real behavioral context: the entire tree returns at once, there is no paging and no search argument, filtering must be done client-side, and it returns categories only (never products or counts). That return-shape disclosure matters because there is no output schema.

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 the core behavior, then routing guidance, then explicit negatives; each sentence earns its place, though the sequence of separate 'never products / no way to list products / say that plainly' statements is slightly redundant.

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?

A zero-parameter, read-only list tool with no output schema is fully covered: the description explains the return shape, the lack of filtering, and where to go for the adjacent product-assignment task.

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?

Zero parameters, so the baseline is 4; the description correctly notes the absence of any search or paging argument, which is the only parameter-relevant fact an agent needs.

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+resource (list the merchant's product categories as a nested tree, sorted by sortOrder) and explicitly distinguishes itself from hub_get_products, hub_create_product and hub_update_product. An agent can tell exactly what this returns without opening any 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?

Gives explicit when-to-use (get the category id any other tool needs), when-not-to-use (this server cannot list a category's products; get_products searches by name/SKU only), and names the alternative tools for the adjacent task (create_product/update_product for assigning categoryIds).

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