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

Annotations already cover the safety profile (readOnly, non-destructive, closed-world), so the bar is lower; the description adds real behavioral context beyond them: the answer is geo-scoped, the call fails closed when country is missing, and the three availability categories that can come back. It stops short of noting caching or coverage limits per region.

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?

Effectively one compact sentence with the availability modes front-loaded and the critical country constraint trailing. No waste, though the interrogative framing is slightly less direct for an agent than an imperative statement would be.

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 only two required parameters, no nested objects, and no output schema, the description carries the needed burden: it explains what the answer means (free vs. subscription vs. external service) and the fail-closed behavior when country is absent. That substitutes well for a missing output schema.

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 both parameters are fully documented in the schema, so the baseline of 3 applies. The description's note that country is required and geo-scoped largely restates the schema's own parameter description rather than adding new 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 names the resource (documentary playability) and enumerates the answer modes the tool returns: free on iWonder, iWonder Plus subscription, or streaming services. It is phrased as a question rather than an explicit verb+resource statement, but an agent can still tell it apart from get_film (metadata) and search_documentaries (discovery) 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?

Usage is implied by the scenario ("can the viewer watch this in their country") and the hard constraint that a country is required and it fails closed without it. However, no sibling is named as an alternative and there is no explicit when-to-use/when-not statement distinguishing this from get_film.

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