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

Annotations already declare readOnly/idempotent/non-destructive, yet the description adds genuinely new behavior: offer categories are kept separate (subscription, free/ad-supported, rental, purchase), rentals/purchases still cost extra even when matched, an empty or stale result does not prove unavailability, and no account is needed for public offers. The personal-access enrichment (streaming_preferences.services, matches_saved_service) is disclosed as a conditional behavior change.

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 workflow, then caveats. Every clause carries information, though a few statements (return field lists) duplicate what the output schema already provides and could be trimmed.

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 the return-field enumeration is partly redundant, but the description still supplies what the schema cannot: auth tiers, ranking preference for included offers, and the unavailability caveat. The main missing piece is any guidance on the country parameter.

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 description adds real meaning for title_ids (ten-item cap, must be exact IDs from search_titles) and corrects the temptation to pass names. However, it never mentions the country parameter or its US default, which is a substantive input the agent must choose deliberately. With reported low schema coverage, that omission leaves a gap.

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 ('Find where to watch a movie or show') and immediately distinguishes scope by including the viewer's saved services. It also names the sibling tool search_titles as the prerequisite resolver, so the agent can place it in the workflow without reading other definitions.

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 guidance: 'Resolve names with search_titles first, then pass up to ten exact IDs', plus a usage rule ('Use saved services without asking the viewer to repeat them') and a framing instruction for presenting included offers. It lacks explicit when-not-to-use conditions, which keeps it below the top score.

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