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

Annotations already mark it read-only/non-destructive, and the description adds context annotations cannot: the MCP Apps picker panel, that the merchant's pick arrives as their next message, and that thumbnailUrl drives that panel's imagery. That is real interaction behavior beyond the safety hints.

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 what a template is and when to call, then the picker behavior. Six sentences is long for a list tool, but nearly all of it carries load; the MCP Apps picker sentence is defensible because it changes how the agent should read the follow-up message.

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?

An output schema exists, so return values needn't be explained, yet the description still tells the agent what each entry contains and how the id feeds create_catalog. Prerequisites, failure mode of the alternative, and UI behavior are all covered — nothing needed to call it 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 coverage is 100% and the single `search` parameter is fully documented in the schema; the description never mentions it. It does add meaning about the returned entries (id, title, products-per-page, thumbnailUrl) and links the id to create_catalog's `template` argument, but input-side semantics are left entirely to the schema.

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 templates a catalog can be built from) and immediately defines what a template supplies — covers, fonts, colours, product-cell layout. This separates it cleanly from siblings like list_images or list_collections, which are also 'list' tools over catalog assets.

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?

Explicit sequencing: 'Use it before create_catalog', plus the consequence of skipping it ('create_catalog without one refuses and returns these same choices') and the irreversibility ('cannot be swapped afterwards without rebuilding'). An agent knows exactly when and why to call this versus going straight to create_catalog.

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