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

Annotations already declare readOnly, idempotent, non-destructive, but the description adds genuinely new behavioral facts: about 30 cards per read, the feed changes through the day, and a read is cached/reused for up to 15 minutes per country and language. It also discloses provenance (home IP in the country, unauthenticated NTA page), which an agent needs to interpret staleness and representativeness of results.

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?

Three sentences, front-loaded with the core action and returned fields, with provenance and caching after. It is dense rather than padded, though the country/language default is stated twice (once narratively, once implicitly in the params) and could be trimmed slightly.

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 usefully enumerates the returned card fields (position, title, publisher, URL, domain, type, age, image) and covers freshness and caching. It does not say what happens for an unsupported or tiny country/language combination (empty feed vs error), which is the main remaining gap.

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 description coverage is 100% and already documents limit (counted from the top, default ~30), country (ISO alpha-2, home IP there), and language (BCP 47, default country language). The description mostly restates these ('in a country, in feed order', 'default feed of that country and language') rather than adding new semantics, so the baseline 3 applies.

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 a specific verb and resource ('The cards Google Discover shows right now in a country, in feed order') and pins down scope with 'with no Google account' and 'not anyone's personal feed and not data from a panel of users'. That implicitly separates it from collect_discover_cards and any personalization tool without needing to name siblings.

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 context is clear: use this for the un-personalized, country/language default feed read from a home IP, not for a user's personal feed or panel data. There is no explicit 'use X instead when…' routing to a named sibling, so it stops short of the top band.

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