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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds genuine behavioral context beyond that: only *active* listings are returned (implying inactive/removed ids will not resolve) and output is localized to the requested language. It stops short of saying what happens on an unknown or inactive id.

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?

A single sentence with zero filler, front-loading the cardinality (one) and the scope (active) before the id source. Nothing could be removed 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 an output schema present, return values need not be explained, and annotations cover the read-only profile, so the short description is nearly sufficient. The only material gap is failure behavior for a missing or inactive listing id.

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 both parameters (listing_id, lang with default null and en/es guidance) are documented in the schema itself. The description reinforces the language parameter ("in the requested language") but adds no format, default, or constraint detail beyond the schema. 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?

"One active listing by id" names a specific resource and scope (single, active), and "(from search_listings)" ties it to the sibling that produces the id. It is a noun phrase rather than an explicit verb, but an agent can still tell it apart from search_listings and send_interest 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 rather than stated: the parenthetical "from search_listings" tells the agent where the id comes from, which is a real routing hint. There is no explicit when-not-to-use or statement of what to do if the listing is not active, so guidance stays at the inferred level.

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