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

Annotations already cover read-only, idempotent, non-destructive, closed-world semantics, so the description's added value is the error contract: a missing id returns found false and explicitly does not substitute another PG. That is a genuinely useful non-obvious behavior no annotation conveys. It stops short of describing pagination or photo limits.

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?

Two sentences, zero filler, with the core identity and returned payload front-loaded and the edge-case behavior appended where it belongs. Every clause carries information an agent cannot get from the schema.

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?

There is no output schema, and the description compensates by enumerating the returned fields, plus it closes the main failure mode (unknown id). For a two-parameter read tool with full annotation coverage, 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 description coverage is 100%, so pg_id and stay_nights are already documented, including the note that stay_nights only affects stay-fit wording. The description mentions only 'by id' and adds no meaning about the stay_nights parameter, so 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?

States a specific verb and resource ('Returns one PG / co-living listing by id') and enumerates exactly what comes back: room types with per-bed rent, move-in costs, monthly extras, house rules, amenities, photos and listing link. The singular 'one ... by id' scope implicitly distinguishes it from the plural search_pg sibling.

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 'by id' phrasing implies this is the follow-up to a search, and the schema note ('PG listing id from search_pg') reinforces that, but the description itself never says when to use this versus search_pg or get_listing. No exclusions or prerequisites are stated, so usage is only implied.

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