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

Annotations already declare readOnlyHint=true, so the safety profile is covered; the description adds genuinely new behavioral facts — that the call is 'Free' (no cost/credit burn) and that each entry carries price, models, an example_url and a slots schema. That is real value beyond the annotation, though it says nothing about result size, ordering, or pagination for a catalog that could grow.

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?

It is front-loaded with the highest-signal token ('Free') and then a scannable id(gloss) enumeration, with the next-step routing saved for last. The middle sentence is a long run-on packing five fields plus slot semantics, which is dense but each clause carries distinct information, so little could be cut without losing meaning.

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, the description carries the full burden of explaining return values and does so: it names the per-entry fields (what it makes, what it delivers, price, models, example_url, slots) and defines the slot contract including the three accepted image input forms. Combined with the template.run handoff, an agent has everything needed to list and then invoke correctly.

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?

The tool takes zero parameters, so the baseline is 4 and there is no parameter surface for the description to compensate for. The description instead spends its words on the shape of the returned slots (name, kind, required, choices, default) and on what image slots accept (asset_key, https URL, data:image), which is useful but belongs to the return value rather than to input semantics.

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 enumerates the exact resource — the media template catalog — and names every template id with a one-line gloss (product-shot, poster, showcase-video, etc.), so an agent knows precisely what it is getting. It also distinguishes itself from the sibling template.run by explicitly deferring execution to it, so the read-vs-run split is unambiguous 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?

The trailing 'NEXT: template.run with a template id and its slots' gives an explicit handoff condition to the alternative sibling, which is exactly the routing an agent needs. It does not state when-not to call this (e.g. if you already know the template id) or mention template.status, so it stops short of full when/when-not coverage.

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